AUTOMATIC 
SCREW  MACHINES 


AUTOMATIC 
SCREW   MACHINES 


AUTOMATIC 
SCREW   MACHINES 


A  TREATISE  ON  THE  CONSTRUCTION,  DE- 
SIGN, AND  OPERATION  OF  AUTOMATIC  SCREW 
MACHINES  AND  THEIR  TOOL  EQUIPMENT 


BY 

DOUGLAS    T.   HAMILTON 

ASSOCIATE  EDITOR  OF  MACHINERY 

AUTHOR  OF  "  AUTOMATIC  SCREW  MACHINE  PRACTICE,"  "  SHRAPNEL 

SHELL  MANUFACTURE,"  "  MACHINE  FORGING,"  "  BOLT, 

NUT,  AND  RIVET  FORGING,"  ETC. 

AND 

FRANKLIN    D.   JONES 

ASSOCIATE  EDITOR  OF  MACHINERY 

AUTHOR  OF  "  TURNING  AND  BORING,"  "  PLANING  AND  MILLING," 
"  GAGING  TOOLS  AND  METHODS,"  ETC. 


FIRST    EDITION 


NEW  YORK 
THE    INDUSTRIAL    PRESS 

LONDON:  THE  MACHINERY  PUBLISHING  CO.,  LTD. 
1916 


COPYRIGHT,  1916 

BY 

THE    INDUSTRIAL   PRESS 
NEW   YORK 


Composition  and  Electrotyping  by  THE  PLIMPTON  PRESS,  Norwood,  Mass 


PREFACE 

THE  class  of  automatic  machine  tools  commonly  known  as 
screw  machines  represents  one  of  the  most  important  develop- 
ments in  the  machine  tool  field,  and  includes  ingenious  mecha- 
nisms which  may  be  studied  with  profit  by  all  who  are  interested 
in  mechanical  movements  and  modern  methods  of  manu- 
facture. This  book  deals  with  five  distinct  branches  of  auto- 
matic screw  machine  practice.  It  covers  the  design  and 
construction  of  different  well-known  types  of  single-  and  mul- 
tiple-spindle machines,  the  tool  equipment  used  for  various 
classes  of  work,  the  methods  of  adjusting  or  setting-up  machines 
made  by  different  manufacturers,  the  design  of  screw  machine 
cams,  and  the  application  of  machines  of  this  type  to  both 
typical  and  unusual  operations.  The  descriptions  of  machines 
are  confined  principally  to  the  important  fundamental  features 
of  the  design,  and  deal  especially  with  those  mechanisms 
which  control  parts  that  must  operate  automatically  and  in 
accordance  with  the  nature  of  the  work  being  produced. 
The  machines  illustrated  were  selected  as  representative  types, 
each  embodying  important  developments  in  screw  machine 
design. 

While  designers  have  incorporated  many  ingenious  ideas 
in  automatic  screw  machines,  the  tool  equipment  and  auxiliary 
attachments  used  in  conjunction  with  these  machines  are  not 
lacking  either  in  cleverness  of  design,  or  effectiveness  in  in- 
creasing the  efficiency  and  range  of  machine  tools  of  this  class, 
to  include  an  endless  variety  of  work.  The  various  types  of 
tools  used  for  turning,  boring,  recessing,  threading,  knurling, 
etc.,  are  described,  and  the  methods  of  applying  these  tools 
are  illustrated  by  practical  examples.  Different  attachments 
are  also  described,  such  as  are  commonly  used  for  slotting 


392309 


vi  PREFACE 

screw-heads,  milling,  cross-drilling,  and  automatically  feeding 
separate  castings  or  forgings  to  the  machine  from  a  magazine. 
Information  on  the  adjustment  and  setting-up  of  screw  ma- 
chines is  given  to  supplement  the  general  descriptions  and 
show  just  what  changes  are  necessary  when  a  machine  must 
be  arranged  for  producing  different  parts.  In  dealing  with 
the  subject  of  cam  design,  the  exact  method  of  laying  out  a 
set  of  cams  for  a  given  operation  has  been  described  in  detail, 
in  order  to  clearly  indicate  the  fundamental  principles 
involved. 

This  treatise  is  intended  especially  for  the  users  of  screw 
machines  and  the  designers  of  tools  and  auxiliary  equipment, 
and,  in  order  to  make  it  of  greater  practical  value  to  the  men 
responsible  for  the  economical  operation  of  these  machines 
and  the  production  of  parts  which  conform  to  required  stand- 
ards of  accuracy,  many  different  classes  of  work  and  a  large 
variety  of  standard  and  special  tools  have  been  described  in 
detail.  The  cooperation  of  screw  machine  manufacturers  in 
supplying  illustrations  and  data  is  much  appreciated. 

THE    AUTHORS. 

NEW  YORK,  September,  1916 


CONTENTS 

CHAPTER  I 

SCREW  MACHINE  CLASSIFICATION  AND 

DEVELOPMENT  PAGES 

Origin  of  the  Term  "Screw  Machine"  —  Distinction 
between  Automatic  and  Semi-automatic  Machines  —  Gen- 
eral Features  of  Automatic  Screw  Machines  — .  Classification 
of  Automatic  Screw  Machines  —  Development  of  Single- 
and  Multiple-spindle  Types  —  General  Application  of  Auto- 
matic Screw  Machines  —  Advantages  of  Single-  and  Mul- 
tiple-spindle Designs i-io 

CHAPTER  II 
SINGLE-SPINDLE  AUTOMATIC  SCREW  MACHINES 

Brown  &  Sharpe  Automatic  Screw  Machine  —  Cleve- 
land Automatic  Screw  Machine  —  Gridley  Single-spindle 
Automatic  Turret  Lathe  —  Chicago  Automatic  Screw 
Machine 11-38 

CHAPTER  III 

MULTIPLE-SPINDLE  AUTOMATIC   SCREW 
MACHINES 

Acme  Four-spindle  Automatic  Screw  Machine  —  Daven- 
port Five-spindle  Automatic  Screw  Machine  —  Hayden 
Five-spindle  Automatic  Screw  Machine  —  Gridley  Four- 
spindle  Automatic  Screw  Machine  —  New  Britain  Six- 
spindle  Automatic  Screw  Machine 39-83 

CHAPTER  IV 

AUTOMATIC   SCREW  MACHINE  TOOL 
EQUIPMENT 

Circular  Forming  and  Cutting-off  Tools  —  Tool-holders 
foi  Flat  Forming  Tools  —  Box-tools  —  Methods  of  Apply- 
ing Box-tool  Cutters  —  Work  Supports  for  Box-tools  — 


Viii  CONTENTS 

Hollow  Mills  —  Centering  and  Facing  Tools  —  Drills  and 
Drill-holders — Counterboring  Tools — Reamers  and  Reamer- 
holders —  Swing  Tools  for  Turning  and  Recessing — Shaving 
Tools  —  Dies  for  Screw  Machine  Work  —  Die-holders  — 
Taps  for  Screw  Machines  —  Knurling  Tools 84-147 


CHAPTER  V 

ADJUSTING  OR  SETTING-UP  AUTOMATIC 
SCREW  MACHINES 

Setting-up  the  Brown  &  Sharpe  Machine  —  Adjustments 
on  the  Cleveland  Automatic  —  Method  of  Setting-up  the 
Acme  Multiple-spindle  Machine  —  Setting-up  the  Daven- 
port Multiple-spindle  Automatic 148-196 


CHAPTER  VI 

ATTACHMENTS  FOR  AUTOMATIC   SCREW 
MACHINES 

Screw  Slotting  Attachment  —  Slotting  and  Slabbing 
Attachment  —  Index  Drilling  Attachment  —  Cross-drilling 
Attachments  —  Turret  Drilling  Attachment  —  Burring  At- 
tachment—  Tap  and  Die  Revolving  Attachment  —  Accel- 
erated Reaming  Attachment  —  Drilling  and  Milling  Attach- 
ment —  Vertical-spindle  Milling  Attachment  —  End-milling 
or  Slotting  Attachment  —  Attachment  for  Forming  Squares 
and  Hexagons  —  Attachment  for  Robbing  Worms  and 
Spiral  Gears  —  Magazine  Feeding  Attachments 197-223 


CHAPTER  VII 
DESIGNING  SCREW  MACHINE  CAMS 

Effect  of  Cutting  Speed  on  Cam  Design  —  General 
Method  of  Designing  Cams  —  Laying  Out  Cams  for  a  Spe- 
cific Operation  —  Development  of  Cam  Lobe  for  Control- 
ling Movement  of  Threading  Die  —  Allowance  for  Tool 
Clearance  —  Use  of  Cam-lever  Templets  —  Laying  Out 
Cams  for  Recessing  —  Cam  Rise  for  Drilling  —  Designing 
Cams  for  Deep-hole  Drilling 224-257 


CONTENTS  IX 


CHAPTER  VIII 

OPERATIONS  ON  SINGLE-  AND  MULTIPLE- 
SPINDLE  SCREW  MACHINES 

Examples  of  Forming  Operations  —  Recessing  —  Drill- 
ing and  Counterboring  from  Cross-slide  —  Making  Watch 
Parts  in  Screw  Machine  —  Examples  of  Work  on  the  Cleve- 
land Automatic  —  Operations  on  Acme  Multiple-spindle 
Machine  —  Use  of  Screw  Machine  for  Producing  and 
Assembling  Parts  —  Thread  Rolling  in  the  Screw  Machine 
-  Different  Types  of  Tools  for  Thread  Rolling  —  Cutting 
Helical  Gears  in  Screw  Machine  —  Speeds  and  Feeds  for 
Screw  Machine  Operation 258-335 


AUTOMATIC    SCREW 
MACHINES 

CHAPTER  I 
SCREW   MACHINE    CLASSIFICATION   AND   DEVELOPMENT 

MACHINE  tools  which  are  either  automatic  or  semi-auto- 
matic in  their  operation  have  replaced  many  hand-operated 
tools,  especially  wherever  large  numbers  of  duplicate  machine 
parts  are  required.  There  are  many  different  classes  of  auto- 
matic machine  tools  used  at  the  present  time,  but  the  most 
important  class  or  group  is  that  which  originated  from  the 
lathe  and  in  which  are  included  the  machines  designed  primarily 
for  turning  and  boring  operations.  In  this  general  class  there 
are  several  distinct  types  which  have  their  own  particular 
field  and  also  many  different  designs. 

The  machines  which  are  dealt  with  in  this  treatise  are 
commonly  known  as  automatic  screw  machines  because  the  work 
for  which  they  were  originally  designed  was  the  making  of 
screws.  This  field,  however,  was  soon  enlarged  to  include  the 
making  of  all  kinds  of  small  nuts,  washers,  pins,  collars,  etc., 
and,  at  the  present  time,  machines  of  this  class  are  capable  of 
a  great  variety  of  operations,  not  only  on  parts  which  are 
turned  from  bars  of  stock,  but  on  separate  castings  or  forgings 
when  magazine  feeding  attachments  are  employed.  It  is 
evident,  therefore,  that  the  term  " screw  machine"  as  applied 
to  modern  machines  of  this  type  is  a  misnomer,  because  the 
making  of  screws  constitutes  only  a  small  part  of  screw  machine 
production.  While  the  smaller  machines  are  naturally  adapted 
to  making  various  kinds  of  standard  and  special  screws,  in 
many  shops  and  factories  they  are  used  almost  exclusively  on 
other  classes  of  work.  The  term  "  screw  machine  "  is  even  less 


2  CLASSIFICATION  AND  DEVELOPMENT 

accurate  or  descriptive  when  applied  to  the  large  automatic 
machines  now  used  extensively  for  general  bar  and  chuck 
work,  in  direct  competition  with  the  semi-automatic  and  hand- 
operated  turret  lathes;  in  fact,  some  manufacturers  of  such 
machines  do  not  list  them  as  screw  machines,  but  as  automatic 
machines,  automatic  turret  lathes,  or  simply  as  "automatics." 

Application  of  the  Term  "  Automatic."  —  The  term  "auto- 
matic," as  applied  to  various  classes  of  machine  tools,  does  not 
always  have  the  same  meaning,  and  a  machine  which  one 
manufacturer  classifies  as  automatic  would  be  considered  semi- 
automatic by  another  manufacturer.  For  instance,  some 
machines  which  are  designed  to  perform  a  certain  cycle  of 
operations,  but  are  not  capable  of  presenting  unfinished  parts 
to  be  operated  upon  to  the  tools,  may  be  referred  to  as  auto- 
matic machines.  While  such  a  machine  is  automatic  or  self- 
moving,  in  that  it  controls  the  movements  of  the  cutting  tools, 
the  attention  of  an  operator  is  required  when  each  part  is  com- 
pleted, so  that  such  a  machine  is  really  semi-automatic. 
There  are  other  types  of  machines,  such  as  the  automatic 
screw  machines,  which  not  only  control  all  the  movements  of 
the  cutting  tools,  but  are  equipped  with  work-feeding  mecha- 
nisms so  that,  when  one  part  has  been  finished,  other  dupli- 
cate parts  may  be  produced  automatically.  The  operation  of 
such  a  machine  is  continuous  until  it  needs  to  be  supplied  with 
raw  material,  which  may  either  be  in  the  form  of  bar  stock, 
or  separate  castings  or  forgings,  when  a  magazine  feeding 
attachment  is  used.  A  machine  of  this  type  is  automatic  in 
the  sense  that  it  repeatedly  performs  all  of  the  necessary 
operations,  which  include  ejecting  the  finished  work  and 
presenting  a  new  piece  or  length  of  stock  to  the  tool. 

From  the  foregoing,  it  will  be  seen  that  the  term  "auto- 
matic" is  a  relative  one  as  applied  to  machine  tools  generally. 
The  early  designs  of  lathes,  after  they  had  been  equipped  with 
self-feeding  mechanisms,  were  automatic  to  the  extent  of 
feeding  the  turning  tool.  As  automatic  feeds  became  the 
rule  rather  than  the  exception,  and  as  additional  automatic 
features  were  incorporated  in  the  designs  of  many  machines, 


GENERAL  FEATURES  3 

the  use  of  the  term  " automatic"  was  no  longer  justified  in 
the  case  of  a  machine  which  simply  had  a  feeding  mechanism. 
According  to  present  usage,  the  term  "automatic"  is  generally 
applied  to  machine  tools  in  which  practically  all  of  the  move- 
ments are  self-actuating,  although,  as  previously  mentioned, 
the  extent  of  the  automatic  operation  varies  considerably  on 
different  machines  which  are  classified  as  automatic  types. 
When  a  machine  is  capable  of  automatically  producing  dupli- 
cate parts  repeatedly,  it  is  universally  referred  to  as  auto- 
matic, whereas,  if  it  simply  performs  a  complete  cycle  of 
machining  operations,  but  requires  the  attention  of  an 
operator  each  time  a  part  is  finished,  it  may  be  'considered 
automatic  by  some,  and  semi-automatic  by  others.  In  some 
cases,  a  machine  of  the  latter  class  is  termed  " automatic," 
while  one  that  is  capable  of  continuous  operation  is  known 
as  "fully  automatic."  In  American  shop  parlance,  the  term 
"automatic"  is  often  used  as  a  noun  to  indicate  any  kind  of 
automatic  turning  machine,  especially  a  screw  machine  or 
automatic  chucking  and  turning  machine  of  the  turret  lathe 
class. 

General  Features  of  Automatic  Screw  Machines.  —  Charac- 
teristic features  of  automatic  screw  machines  in  general  are 
means  for  automatically  locating  successive  tools  in  the  cor- 
rect working  position,  the  automatic  changing  of  feeds  and 
speeds  to  secure  economical  operation,  and  the  presenting  of 
new  stock  to  the  tools  for  a  similar  series  of  operations.  These 
various  movements,  which  are  entirely  automatic,  are  obtained 
principally  from  cams  which  are  rotated  at  predetermined 
speeds  and  are  so  formed  and  set,  relative  to  one  another, 
that  the  parts  of  the  machine  which  they  control  all  operate 
at  the  proper  time  and  at  suitable  feeds  or  speeds. 

There  are  two  general  methods  of  presenting  new  stock  or 
raw  material  to  the  tools  so  that  the  machine  can  produce 
duplicate  parts  automatically.  In  most  cases,  the  stock  is 
in  the  form  of  a  bar  which  is  large  enough  in  diameter  to  allow 
for  making  parts  of  the  required  size.  This  bar  is  held  in  the 
hollow  rotating  spindle  of  the  machine  and,  as  soon  as  the  tools 


4  CLASSIFICATION  AND  DEVELOPMENT 

have  finished  one  part,  the  bar  is  automatically  pushed  forward 
far  enough  for  making  another  piece.  After  the  bar  is  fed 
forward,  it  is  held  firmly  by  a  suitable  chuck  in  the  end  of  the 
spindle  and  the  different  tools  advance  in  the  proper  order, 
perform  their  respective  machining  operations,  and  then  recede. 
When  the  finished  piece  has  been  cut  from  the  bar,  the  latter 
is  again  pushed  forward  against  a  stop  which  regulates  the 
distance  that  it  projects  beyond  the  chuck,  and  the  cycle  of 
operations  is  repeated  until  the  entire  bar  has  been  used  and 
changed  into  the  finished  product.  The  attendant,  who  is 
able  to  care  for  quite  a  number  of  machines,  then  inserts 
a  new  bar. 

While  most  of  the  parts  produced  in  automatic  screw 
machines  are  made  from  bar  stock,  many  castings  and  drop- 
forgings  may  also  be  finished  in  machines  of  this  class.  When 
each  part  is  a  separate  unit,  some  auxiliary  feeding  mechanism 
must  be  employed  for  automatically  inserting  the  rough  pieces 
into  the  chuck,  preparatory  to  the  machining  operations. 
These  magazine  feeding  mechanisms  or  attachments  are  loaded 
or  filled  with  the  parts  that  require  machining  and  are  so  de- 
signed and  adjusted  that  a  rough  piece  is  transferred  from 
the  magazine  to  the  spindle  chuck,  after  the  tools  have  com- 
pleted their  work  and  the  part  finished  previously  has  been 
ejected.  These  magazine  feeding  attachments  vary  in  design, 
according  to  the  shape  of  the  work  and  the  nature  of  the 
machining  operation.  Magazine  attachments  are  used  for  that 
class  of  work  which  cannot  be  produced  profitably  from  bar 
stock,  either  because  of  irregularity  of  shape  or  the  amount  of 
material  which  would  have  to  be  removed. 

Classification  of  Automatic  Screw  Machines.  —  There  are 
two  general  classes  of  automatic  screw  machines,  known  as 
single-spindle  and  multiple-spindle  types,  respectively.  The 
single-spindle  machines  operate  on  one  part  at  a  time,  as  there 
is  only  one  work-holding  spindle.  For  instance,  when  operat- 
ing on  a  bar  of  stock,  the  tools  perform  whatever  turning, 
drilling,  reaming,  counterboring,  threading,  or  other  operations 
may  be  necessary,  and  then  the  finished  piece  is  cut  off;  hence, 


SCREW   MACHINE  DEVELOPMENT  5 

the  time  required  to  complete  a  part  on  a  single-spindle  ma- 
chine is  equal  to  the  total  time  necessary  for  all  of  the  separate 
operations,  which  includes  the  time  for  withdrawing  the  tools 
at  the  completion  of  the  various  cuts,  indexing  the  turret  which 
holds  the  tools,  and  presenting  the  succeeding  tools  to  the 
work. 

The  multiple-spindle  machine  is  designed  to  operate  on 
several  parts  at  the  same  time.  Thus,  if  a  four-spindle  machine 
is  turning  parts  from  bar  stock,  each  spindle  holds  and  rotates 
a  bar  which  is  operated  upon  by  one  or  more  tools,  and  the 
spindle  carrier  or  head  indexes  or  turns  one-fourth  revolu- 
tion as  the  tools  at  the  four  positions  or  stations  recede  after 
completing  their  work.  With  this  arrangement,  each  bar  is 
successively  located  in  front  of  the  different  tools  and  a  part 
is  finished  at  each  indexing.  It  is  evident,  therefore,  that  a 
multiple-spindle  machine  is  practically  several  machines  con- 
tained in  one  unit,  and  the  total  time  required  to  complete 
a  part  is  equal  to  the  time  necessary  for  the  longest  single 
operation  plus  the  time  for  the  idle  movements.  In  some 
cases,  the  time  may  be  reduced  considerably  by  dividing  the 
longest  operation  into  two  operations.  For  instance,  when 
a  comparatively  long  length  needs  to  be  turned,  instead  of 
using  one  box-tool,  the  cut  is  often  divided  between  two  tools 
held  in  the  first  and  second  positions.  The  drilling  of  a  rather 
deep  hole  is  frequently  divided  in  the  same  way,  by  using  two 
or  three  drills  located  in  different  positions. 

Development  of  Single-spindle  Machine.  —  The  screw 
machine  was  developed  to  a  state  of  practical  usefulness 
principally  by  Christopher  M.  Spencer.  With  the  intro- 
duction of  the  original  Spencer  automatic  screw  machine 
in  the  early  eighties  began  the  extensive  use  of  " automatics" 
as  an  important  factor  in  modern  machine-shop  practice. 
This  machine  was  simply  a  small  turret  lathe  or  "  screw  ma- 
chine" fitted  with  a  modified  form  of  the  Parkhurst  wire  or 
rod  feed;  but  the  various  motions  usually  operated  by  hand 
were  controlled  instead  from  various  cams  on  a  single  cam- 
shaft, extending  under  the  machine  for  its  whole  length. 


6  CLASSIFICATION  AND  DEVELOPMENT 

Changes  in  feed  and  length  of  cut  were  made  by  changes  in 
simple  strap  cams.  .The  time  taken  for  the  idle  movements 
was  shortened  by  giving  a  quick  movement  to  the  camshaft, 
automatically  changing  to  the  slow  feeding  movement  when 
the  cutting  tools  approached  the  work.  Machines  of  practi- 
cally the  original  design  are  still  in  successful  use. 

The  first  automatic  screw  machine  to  depart  from  the 
Spencer  type  was  the  one  built  by  the  Brown  &  Sharpe  Manu- 
facturing Co.  This  machine  employs  disk  cams,  which  are 
usually  special  for  the  particular  piece  being  made.  Unlike 
the  Spencer  machine,  these  cams  have  a  rotating  motion  at 
a  uniform  speed,  all  the  idle  movements  being  operated  by 
intermittent  clutch  connections  with  a  fast-running  controll- 
ing shaft.  The  machine  is  noted  for  its  accuracy  and  for  the 
quickness  of  its  motions  and  is  familiar  to  all  screw-machine 
specialists.  As  is  the  case  with  most  of  the  modern  machines, 
it  may  be  fitted  with  various  automatic  attachments  for  milling, 
cross-milling,  screw  slotting,  etc. 

The  automatic  field  has  been  greatly  extended  by  the  de- 
velopment of  the  heavier  class  of  automatic  machines,  such  as 
the  Gridley,  Cleveland,  and  Chicago,  which  have  made  it 
possible  to  produce  comparatively  large  work  that  formerly 
could  only  be  done  on  an  engine  lathe  or  that  type  of  turret 
lathe  designed  for  handling  bar  stock. 

Development  of  Multiple-spindle  Machine.  —  While  the 
machines  previously  referred  to  have  led  in  widening  .  the 
field  of  the  "automatic,"  there  has  been  another  line  of 
development  which  has  greatly  increased  production  in  those 
classes  of  work  for  which  screw  machines  were  first  used. 
This  is  the  multiple-spindle  automatic  screw  machine  which 
was  originated  by  Reinhold-Hackewessell  and  E.  C.  Henn. 
The  first  successful  design  was  built  by  the  National  Acme 
Mfg.  Co.  In  this  machine,  the  turret  is  dispensed  with,  and 
its  place  is  taken  by  a  tool-holder  which  feeds  tools  forward 
to  operate  on  bars  of  stock  held  in  four  opposing  work-spindles. 
It  is  a  drum  or  carrier  containing  these  spindles  which  "  in- 
dexes/7 instead  of  the  tool-holder  or  turret.  After  the  tool- 


GENERAL  APPLICATION  7 

holder  has  concluded  its  working  stroke  and  retired,  the 
work -spindle  carrier  or  head  is  revolved,  bringing  each  bar  of 
stock  to  the  next  tool  in  rotation.  The  final  tool  position  pro- 
vides for  a  cut-off  blade,  and  a  complete  piece  is  finished  and 
cut  off  at  each  indexing.  One  or  more  forming  slides  also 
operate  at  the  different  spindle  positions  if  necessary.  With 
this  type  of  machine,  all  the  cutting  tools  are  working  on  each 
feeding  stroke,  as  each  has  a  bar  of  stock  presented  to  it, 
whereas,  with  a  single-spindle  machine,  the  various  tools  of 
the  turret  operate  successively  on  a  single  bar  of  stock. 

Among  other  well-known  designs  of  multiple-spindle 
machines  may  be  mentioned  the  Davenport,  Gridley,  New 
Britain,  and  the  Hayden  machines.  These  various  designs, 
which  will  be  described  later,  each  possess  distinctive  features 
and  represent  ingenious  examples  of  modern  machine-tool 
development. 

General  Application  of  Automatic  Screw  Machines.  —  Auto- 
matic screw  machines  are  used  for  such  a  variety  of  operations 
that  only  a  general  outline  of  the  work  for  which  they  are 
adapted  can  be  given.  As  previously  mentioned,  machines 
of  this  class  are  designed  primarily  for  producing  parts  from 
bars  of  stock,  although  by  the  addition  of  auxiliary  attach- 
ments they  may  also  be  used  for  machining  separate  forgings 
or  castings.-  The  work  done  on  a  screw  machine  usually 
involves  such  operations  as  turning,  drilling,  reaming,  boring, 
recessing,  counterboring,  and  threading.  In  order  to  avoid  a 
secondary  operation  on  another  machine,  attachments  are 
also  used  which  enable  special  operations  to  be  performed. 
For  instance,  if  a  screw  or  pin  requires  a  hole  drilled  through 
the  head  in  a  cross-wise  direction,  a  cross-drilling  attachment 
is  used.  There  are  also  attachments  for  cutting  the  slots  in 
screw-heads  after  the  screws  have  been  turned  and  threaded 
by  the  regular  mechanism  and  tool  equipment  of  the  machine, 
and  other  ingenious  attachments  have  been  designed  to  in- 
crease the  range  of  automatic  screw  machines  and  make  it 
possible  to  completely  finish  parts  on  them  in  one  series  of 
operations.  These  attachments  are  separate  units  and  are 


8  CLASSIFICATION  AND   DEVELOPMENT 

applied  to  the  machine  in  such  a  way  that  they  operate  in 
conjunction  with  the  regular  tools. 

The  extent  of  the  tool  equipment  and  its  cost  naturally 
depends  upon  the  nature  of  the  work.  For  many  operations, 
only  standard  tools,  such  as  box- tools,  reamers,  dies,  etc.,  are 
necessary.  Frequently  an  additional  special  tool  is  needed, 
such  as  a  forming  tool  for  turning  the  head  of  a  pin  or  screw 
to  an  irregular  shape,  and  sometimes  several  special  tools  are 
necessary.  The  cost  of  the  tool  equipment  for  producing  a 
certain  part  is  often  an  important  item.  When  a  very  large 
number  of  duplicate  parts  are  required,  expense  for  special 
tools  is  of  less  importance  than  when  a  relatively  small  number 
of  pieces  are  to  be  made.  In  many  cases,  it  is  difficult  to  de- 
cide whether  an  automatic  screw  machine  should  be  used, 
or  some  other  machine,  such  as  a  semi-automatic  turret  lathe 
or  a  hand-operated  turret  lathe  or  screw  machine.  It  is  im- 
portant to  consider  the  number  of  parts  required  and  the  rela- 
tion between  the  higher  rate  of  production  obtained  with  the 
automatic  machine,  the  relative  cost  of  tools  for  each  machine, 
and  the  time  necessary  for  adjusting  or  setting  up  the  ma- 
chine. A  general  idea  of  the  different  points  that  should  be 
considered  in  determining  the  conditions  favorable  to  the  use 
of  automatic  screw  machines  may  be  obtained  by  studying 
the  various  machines,  tools,  attachments,  and  operations  re- 
ferred to  in  the  following  chapters. 

Advantages  of  Single-  and  Multiple-spindle  Designs.  - 
The  difference  in  the  rate  of  production  between  the  single-  and 
multiple-spindle  types  of  screw  machines  varies  considerably 
on  different  classes  of  work.  When  comparing  the  two  types, 
there  are  two  important  points  to  be  considered;  i.  The  rela- 
tive rates  of  production  for  the  general  class  of  work  required. 
2.  The  degree  of  accuracy  necessary  in  connection  with  the 
finished  product.  In  general,  multiple-spindle  machines  are 
greatly  superior  so  far  as  rate  of  production  is  concerned,  but 
as  a  general  rule  they  are  not  capable  of  such  extremely  accu- 
rate results  as  well-designed  and  carefully  constructed  single- 
spindle  machines.  While  well-built  multiple-spindle  machines 


GENERAL  APPLICATION  9 

will  produce  very  accurate  work,  it  is  generally  considered 
impracticable  in  a  commercial  machine  to  secure  the  same 
degree  of  accuracy  as  with  a  single-spindle  design,  assuming 
that  each  type  of  machine  is  constructed  in  accordance  with 
approved  methods.  It  is  more  difficult  to  secure  accurate 
indexing  with  multiple-spindle  machines  than  with  the  single- 
spindle  types,  because  of  the  greater  mechanical  difficulties 
of  constructing  a  machine  having  several  spindles  which  are 
equally  spaced  and  equi-distant  from  the  axis  of  the  spindle 
carrier.  In  order  to  overcome  any  slight  inaccuracies  which 
may  exist,  ingenious  methods  of  locating  the  spindle  carriers 
have  been  devised  and  the  degree  of  accuracy  obtainable  on 
high-grade  machines  of  multiple-spindle  design,  is  sufficient 
for  all  except  the  most  exacting  work. 

Each  type  of  machine  has  its  own  field,  although  it  is  impos- 
sible to  draw  a  definite  line  which  indicates  just  where  one 
type  is  superior  to  the  other.  The  rate  of  production  is  not 
always  in  favor  of  the  multiple-spindle  design.  For  instance, 
when  turning  small  brass  parts,  etc.,  a  very  fast  spindle  speed 
is  required  to  secure  an  efficient  cutting  speed,  and  a  light 
single-spindle  machine  is  especially  adapted  to  fast  speeds, 
whereas,  with  the  multiple-spindle  type,  it  is  not  practicable 
to  operate  the  spindles  so  rapidly,  because  of  the  geared  drive 
to  each  spindle;  consequently,  for  a  given  rate  of  feed,  the 
tools  on  a  high-speed,  single-spindle  machine  cut  faster  and 
also  withdraw  and  index  with  great  rapidity.  With  a  mul- 
tiple-spindle machine,  the  indexing  movements  are  somewhat 
slower  because  all  of  the  work  spindles,  the  spindle  carrier, 
and  the  bars  of  stock  must  be  indexed,  and,  owing  to  their 
combined  weight,  there  is  considerable  inertia  to  overcome 
when  the  indexing  movement  is  started  and  it  is  also  necessary 
to  arrest  the  movement  of  the  spindle  head  without  injurious 
shocks;  hence  a  slower  indexing  movement  is  necessary. 
When  turning  brass  or  small  steel  parts,  especially  when  there 
are  no  long  operations,  such  as  turning  long  surfaces  or  drilling 
deep  holes,  and  the  idle  time  represents  a  comparatively  large 
percentage  of  the  total  time,  the  importance  of  rapid  move- 


10  CLASSIFICATION  AND  DEVELOPMENT 

ments  is  apparent,  and  while  the  single-spindle  machine  must 
index  for  locating  each  turret  tool,  whereas  with  the  multiple- 
spindle  machine  a  part  is  completed  for  each  indexing  move- 
ment, this  handicap  is  overcome  on  some  classes  of  work. 
When  there  are  long  turning  or  drilling  operations,  or  in  case 
considerable  material  must  be  removed  by  forming  tools,  the 
multiple-spindle  design  has  a  decided  advantage  as  compared 
with  the  single-spindle  type,  because  the  tools  all  operate 
together  and  the  time  for  the  longest  operation  can  be  reduced 
one-half  by  using  two  tools  simultaneously. 

The  advantages  of  each  type,  as  outlined  in  the  foregoing, 
are  subject  to  wide  variations,  owing  to  differences  in  the  de- 
sign, the  size  of  the  machines,  and  the  nature  of  the  work. 
For  instance,  some  multiple-spindle  machines  are  designed 
especially  for  small  work  and  index  very  rapidly,  one  well- 
known  make  requiring  only  one  second  for  the  indexing  move- 
ment, during  which  time  the  chucks  are  opened,  the  stock  fed 
forward  against  a  stop,  the  chucks  closed,  and  the  feed-tube 
drawn  back  ready  for  the  next  feeding  movement.  The  maxi- 
mum capacity  of  this  machine  is  for  ^-inch  round  stock.  Mul- 
tiple-spindle machines  of  larger  sizes  require  more  time  for 
indexing.  The  single-spindle  type  covers  a  much  wider  range 
of  work  as  to  size,  some  machines  being  adapted  to  the  turning 
of  small  watch  and  clock  parts,  whereas  others  are  capable  of 
handling  bars  of  stock  6  or  7  inches  in  diameter;  in  fact,  one 
single-spindle  machine  (the  Cleveland  Automatic)  has  a 
maximum  capacity  of  7!  inches. 


CHAPTER  II 
SINGLE-SPINDLE   AUTOMATIC    SCREW   MACHINES 

AUTOMATIC  screw  machines,  in  common  with  all  machines 
of  the  self-acting  type,  are  naturally  more  complicated  than 
those  types  which  require  a  certain  amount  of  hand-manipula- 
tion, and,  in  order  to  understand  the  methods  of  adjusting 
and  using  such  machines,  it  is  essential  to  know  just  how  the 
automatic  action  is  obtained.  While  the  automatic  screw 
machines  made  by  different  manufacturers  all  differ  in  regard 
to  details  of  design,  the  general  principle  upon  which  machines 
of  the  same  class  operate  is  practically  the  same  in  each  case. 
The  different  methods  of  controlling  the  various  movements  and 
adjustments  for  the  tools,  however,  differ  considerably  on  some 
machines,  and  a  study  of  these  important  features  will  prove  of 
value  to  anyone  desiring  a  knowledge  of  screw-machine  con- 
struction and  operation.  In  this  chapter,  representative  types 
of  single-spindle  automatic  screw  machines  are  described. 
Other  machines  of  the  multiple-spindle  design  are  referred  to 
in  the  following  chapter. 

Brown  &  Sharpe  Automatic  Screw  Machines.  —  The  auto- 
matic screw  machine  shown  in  Fig.  i  is  made  by  the  Brown  & 
Sharpe  Mfg.  Co.  and  is  intended  for  comparatively  small 
work.  The  bar  of  stock  to  be  operated  upon  is  inserted  through 
the  hollow  spindle  of  the  machine.  This  spindle  is  driven  from 
an  overhead  countershaft  by  means  of  open  and  cross  belts 
operating  on  the  friction  pulleys  A  and  B.  When  one  pulley 
is  engaged  by  the  clutch,  a  forward  movement  for  turning 
operations  is  obtained,  and  a  reverse  movement  for  backing 
off  a  die  when  threading  is  secured  when  the  other  pulley  is 
engaged.  For  ordinary  operations,  the  necessary  tools  are 
held  in  the  turret  /  and  on  front  and  rear  cross-slides  at  E. 

ii 


12 


SINGLE-SPINDLE  DESIGNS 


J L 


F 


BROWN  &   SHARPE   SCREW  MACHINE  13 

There  are  six  holes  in  the  turret  and  all  or  part  of  these  holes 
may  contain  tools,  the  number  depending,  of  course,  upon  the 
extent  of  the  operations.  A  stop  for  regulating  the  distance 
that  the  stock  is  fed  through  the  spindle  after  each  finished  part 
is  severed  from  the  bar  is  held  in  the  turret  and,4  in  addition, 
such  tools  as  a  hollow  mill,  a  box-tool,  a  threading  die,  etc. 
In  case  a  forming  operation  is  necessary,  the  forming  tool  is 
held  on  one  cross-slide  and  the  cutting-off  tool  on  the  other. 

All  feeds  and  other  movements  of  the  machine,  except  the 
rotation  of  the  spindle,  are  derived  from  the  feed-shaft  O3 
(Fig.  2)  at  the  rear  of  the  machine,  which,  in  turn,  is  driven  by 
a  belt  from  an  overhead  countershaft  operating  on  pulley  C. 
All  of  the  operations  are  timed  or  regulated  from  camshafts 
on  the  front  and  end  of  the  bed.  These  shafts  are  driven  from 
the  constant-speed  feed-shaft  03  at  the  rear,  through  a  worm- 
wheel  and  change-gears  H  located  at  the  end  of  the  bed.  By 
means  of  these  change-gears,  the  duration  of  the  cycle  of 
operations,  or  the  length  of  time  required  to  make  one  piece, 
is  positively  regulated.  The  operations  of  feeding  the  stock, 
reversing  the  spindle,  and  indexing  the  turret  are  regulated 
by  trip  dogs  or  carriers  on  the  camshaft  D  at  the  front  of  the 
machine,  the  adjustment  of  the  dogs  serving  to  accurately 
time  the  successive  operations.  These  dogs  operate  levers 
which  extend  through  the  machine  bed  to  the  rear  shaft  Oa, 
where  they  connect  with  and  operate  positive  clutches  at  the 
right  time.  The  tripping  of  a  lever  by  a  dog  engages  the  cor- 
responding clutch,  thus  causing  gears  or  a  face-cam  to  revolve 
with  the  feed-shaft  03.  In  this  way,  motion  is  obtained  for 
performing  a  certain  operation,  and  then  the  clutch  auto- 
matically releases.  If  more  work  is  to  be  done  than  can.be  per- 
formed by  a  single  operation,  such  as  feeding  extra  lengths 
of  stock  or  passing  empty  holes  in  the  turret,  several  dogs  or 
a  special  dog  can  be  used  so  that  the  same  operation  is 
performed  several  times  in  rapid  succession. 

The  turret-slide  and  cross-slides  are  fed  to  the  work  by  the 
action  of  disk  cams  and  levers,  each  slide  having  a  separate 
cam  or  three  cams  in  all.  One,  two,  or  sometimes  three  pieces 


SINGLE-SPINDLE  DESIGNS 


BROWN  &   SHARPE   SCREW  MACHINE  15 

of  work  are  completed  in  one  revolution  of  a  cam  so  that  the 
various  movements  of  one  of  the  slides,  in  making  a  particular 
piece,  are  laid  out  as  curves  around  the  cam;  the  curves  for 
one  piece  include  the  whole  circumference,  whereas  for  two  or 
three  pieces  they  are  repeated.  Special  cams  are  required 
for  each  job,  and  these  must  be  laid  out  in  accordance  with  the 
nature  of  the  work,  as  described  in  Chapter  VII. 

Stock-feeding  and  Chuck-operating  Mechanism.  —  The 
stock  is  automatically  advanced  through  the  spindle  after 
successive  parts  have  been  formed  and  cut  off  in  the  machine 
shown  in  Fig.  i,  by  means  of  a  feed-tube  extending  through 
the  spindle.  This  feed-tube  has  spring-feeding  fingers  that  are 
located  at  the  rear  of  the  collet  chuck.  The  tube  may  be 
withdrawn  and  the  fingers  readily  changed  for  different  sizes 
of  stock.  The  motion  for  feeding  the  stock  is  derived  from 
cam  E2  (Fig.  i).  This  cam  actuates  a  slide  through  a  lever 
that  engages  a  block  that  may  be  adjusted  by  crank  N  (Fig.  2) 
for  varying  the  feeding  movement.  The  feed-tube  is  connected 
to  the  slide  by  means  of  a  latch  that  may  be  raised,  thus  allow- 
ing the  feed  to  remain  idle  or  the  tube  to  be  withdrawn. 

The  opening  and  closing  of  the  collet  is  controlled  by  another 
cam  surface  on  cam  E2.  The  action  of  this  cam  is  controlled 
by  dogs  on  drum  K  which  serve  to  engage  or  disengage  a  clutch 
through  which  the  cam  is  rotated.  When  the  chuck  is  closed 
upon  the  stock,  the  feeding  fingers  are  withdrawn  preparatory 
to  the  next  forward  feeding  movement.  The  feeding  mecha- 
nism derives  its  motion  from  the  rear  shaft  03  (Fig.  2)  through 
spur  gearing  at  F2. 

Operation  of  the  Cross-slides.  —  The  front  and  rear  cross- 
slides  are  independent  and  may  be  used  together  or  separately. 
They  are  operated  by  disk  or  plate  cams  C/2  and  F2  mounted 
on  the  front  camshaft  D,  Fig.  i.  The  front  cross-slide  is  oper- 
ated by  segment  lever  Wz,  Fig.  3,  the  teeth  of  which  mesh  with 
rack  F2.  This  rack  is  threaded  on  one  end  and  has  an  adjust- 
ing nut  A  3  which  is  used  for  changing  the  position  of  the  cross- 
slide  relative  to  the  center  of  the  spindle.  The  rear  cross-slide 
is  operated  through  a  double  lever  or  segment  gear  B3)  which 


i6 


SINGLE-SPINDLE  DESIGNS 


connects  with  a  rack,  as  the  illustration  shows.  The  cross- 
slides  are  made  to  travel  to  exactly  the  same  point  by  set-screws 
€3,  which  come  into  contact  with  stops  Z)3.  The  cross-slide 
tools  are  circular  in  form  and  are  attached  to  suitable  holders 
by  screw  1 3. 

Operation    of    the    Turret-slide.  —  The    turret    7,    Fig.    i, 
which  carries  the  end-working  tools,  is  mounted  in  a  vertical 


Mfahtnery 


Fig.  3.   Partial  Section  of  No. 


0  Machine  showing  Mechanism  for  Operating 
Cross-slides 


plane  so  that  it  rotates  about  a  horizontal  axis.  This  position 
allows  the  tools  to  work  closely  in  between  the  cross-slide 
tools  with  a  minimum  of  overhang,  and  the  idle  tools  do  not 
interfere  with  the  cross-slide.  The  turret-slide  is  mounted 
directly  on  the  machine  bed  and  the  turret  is  rotated  or  in- 
dexed to  bring  the  different  tools  into  the  working  position, 
by  means  of  hardened  roll  C4  (Fig.  4)  attached  to  disk  D4- 
This  roll  engages  radial  grooves  in  the  disk  E4.  The  disk  D± 


BROWN  &   SHARPE   SCREW  MACHINE 


is  driven  from  the  rear  driving  shaft  through  spur  and  helical 
gearing,  and  makes  six  revolutions  for  every  revolution  of  the 
turret. 

The   turret  is   locked   in  position  by   the   hardened   taper 
plug  /4  which  is  operated  by  latch  L4,  controlled  by  a  cam  MI 


ftl     J -Jj'"-,i  ""•  I  •      ji| -i   '  |    [  I  ^V— -^ 

Cli-—---^f  |  nri__~|ipj'~ril    I     n  LJJ  J  n\l 


REAR  DRIVING  SHAFT 


Machinery 


Fig.  4.   Plan  and  Rear  Elevation  of  Turret-slide  and  its  Operating  Mechanism 

on  the  end  of  shaft  _V4.  The  slide  G  carrying  the  turret  re- 
ceives its  forward  movement  through  a  "lead  cam"  which 
transmits  motion  through  the  segment  lever  O4.  The  shaft 
carrying  the  lead  cam  is  driven  from  the  rear  driving  shaft 
through  worm  and  spur  gearing.  The  turret-slide  is  returned 
by  a  coil  spring  S4.  The  rapid  return  and  advance  of  the 
turret-slide  and  the  indexing  of  the  turret  are  controlled  in- 


l8  SINGLE-SPINDLE  DESIGNS 

dependency  of  the  lead  cam  by  a  crank  TF4  which  is  connected 
eccentrically  to  the  turret  revolving  shaft  F4.  This  crank 
indexes  the  turret  while  the  roll  on  the  bell  crank  lever  O4  is 
passing  from  the  highest  point  of  the  lead  cam  to  the  starting 
point  of  the  lobe  for  the  next  cut.  Crank  W \  is  driven  from 
the  rear  driving  shaft  by  a  positive  clutch,  the  latter  being 
operated  by  tripping  levers  and  dogs  on  drum  /,  Fig.  i. 

Automatic  Spindle  Speed  Changes.  —  The  speed  changes 
for  the  spindle  are  made  by  shifting  a  belt  on  cone-pulleys 
forming  part  of  the  overhead  works.  For  each  change  so 
obtained  on  the  two  larger  machines,  two  spindle  speeds  are 
available,  one  of  which  is  fast  and  one  slow.  The  change  is 
made  automatically  and  is  controlled  by  an  adjustable  trip 
dog.  This  automatic  change  of  speed  is  of  especial  value  in 
threading,  one  speed  being  employed  for  turning  and  a  slower 
speed  for  cutting  the  thread. 

Operation  of  the  Deflector.  —  In  order  to  separate  the  chips 
and  oil  from  the  finished  parts  which  are  cut  off  from  the  bar, 
a  deflector  is  used.  This  deflector  is  located  on  the  end  of  a 
lever  that  is  actuated  by  a  cam-block  mounted  on  the  drum  K, 
Fig.  i.  Before  the  finished  part  is  severed,  this  cam-block 
causes  the  deflector  to  move  under  the  chute  of  the  machine 
so  that,  when  the  work  falls,  it  strikes  the  deflector  and  enters 
a  suitable  receptacle,  instead  of  falling  into  the  pan  containing 
the  chips. 

Reversal  of  Spindle  for  Threading.  —  The  reversal  of  the 
spindle  for  backing  off  a  die  or  removing  a  tap  from  a  hole 
is  obtained  by  means  of  a  clutch  mechanism,  located  between 
the  two  belt  pulleys  A  and  B,  which  revolve  in  opposite  direc- 
tions. The  clutch  bodies,  which  are  conical,  are  forced  into 
conical  seats  in  the  pulleys  by  a  sliding  collar  located  between 
the  clutch  bodies  on  the  spindle.  This  collar  is  operated  by 
a  lever  and  cam  beneath  the  spindle.  On  the  No.  oo  machine, 
the  spindle  is  reversed  by  means  of  a  spring  plunger  F,  Fig.  2, 
and  on  the  Nos.  o  and  2  machines,  by  a  cam  A2.  The  spring 
plunger  F,  when  released,  instantly  engages  the  cone  of  the 
clutch  with  pulley  A,  thus  rotating  the  spindle  backward. 


CLEVELAND  AUTOMATIC 


20  SINGLE- SPINDLE  DESIGNS 

To  run  forward,  the  clutch  is  shifted  by  the  cam  A2,  to  engage 
pulley  B,  which  revolves  in  the  opposite  direction.  This  cam 
A  2  is  actuated  by  clutch  B2  which  is  operated  by  a  lever  that 
is  controlled  by  a  dog  held  on  drum  L  on  the  front  camshaft. 
Several  sets  of  trip  dogs  can  be  used  on  the  drum  or  carrier 
for  reversing  the  spindle,  when  more  than  one  thread  is  desired 
on  a  piece.  The  carrier  for  controlling  the  reverse  movement 
may  be  disconnected  by  pulling  out  a  knob,  thus  allowing  it 
to  remain  idle  when  work  is  to  be  done  which  does  not  require 
threading. 

The  Cleveland  Automatic  Machine.  —  The  automatic  screw 
machines  which  were  originally  designed  for  making  small 
screws  and  later  for  miscellaneous  small  parts  have  led  to  the 
development  of  automatic  machines  capable  of  turning  an 
endless  variety  of  comparatively  large  and  heavy  parts.  One 
of  the  Cleveland  automatic  machines  is  shown  in  Figs.  5  and  6. 
This  particular  machine  will  operate  on  bar  stock  3!  inches 
in  diameter,  and  similar .  designs  are  built  in  various  sizes, 
one  of  which  has  a  chuck  capacity  of  yf  inches. 

In  addition  to  the  full  automatic  type  shown  in  Figs.  5  and 
6,  which  is  known  as  "  Model  A,"  the  Cleveland  automatic 
is  also  built  in  several  other  types.  The  "full  automatic" 
machine  is  provided  with  a  turret  having  five  holes,  on  sizes 
from  f  to  2\  inches,  inclusive,  and  six  holes  on  the  machines 
of  greater  capacities.  The  next  type  of  machine  is  the  plain 
automatic,  known  as  "Model  B."  This  machine  has  no 
turret,  but  is  provided  with  one  tool  spindle  which  can  be 
used  for  holding  a  box-tool,  drill,  or  similar  tools.  The  range 
of  this  machine  can  be  greatly  increased  by  the  addition  of 
simple  attachments  on  the  cross-slides  and  tool  spindle.  The 
Model  C  machine  is  of  the  full  automatic  type  and  is  halfway 
between  Models  A  and  B.  It  is  provided  with  only  three 
holes  in  the  turret  and  resembles  Model  B  in  construction. 
The  type  of  machine  known  as  "  Model  D  "  is  similar  to  Model 
A,  but  is  built  to  handle  castings,  forgings,  etc.,  and  is  semi- 
automatic in  its  operation.  The  double-spindle,  plain  auto- 
matic is  a  modification  of  the  plain  machine  and  is  provided 


CLEVELAND  AUTOMATIC 


21 


22  SINGLE-SPINDLE   DESIGNS 

with  two  opposing  work-spindles  located  in  a  parallel  line  and 
with  the  chuck  mechanism  of  both  heads  acting  simultane- 
ously. This  machine  is  particularly  adapted  for  finishing  both 
ends  of  a  piece  of  work,  thus  obviating  the  necessity  of  a  second 
operation  to  complete  the  part. 

Spindle  Driving  Mechanism.  —  The  work-spindle  A  of  the 
machine  shown  in  Figs.  5  and  6  is  driven  from  the  overhead 
countershaft  by  means  of  two  pulleys,  B  and  C,  which  trans- 
mit motion  to  the  spindle  through  gearing.  Between  the  pul- 
leys B  and  C  there  is  a  loose  or  idler  pulley.  The  outer  pulleys 
B  and  C  may  both  be  rotated  in  one  direction,  thus  giving  two 
speeds,  or  one  may  be  given  a  reverse  movement  for  threading 
operations.  The  shifting  of  the  driving  belt  from  one  pulley 
to  another  is  effected  by  a  belt  shifter  V.  The  shifting  device 
is  operated  by  means  of  cam  fingers  7i  (see  Fig.  8)  which  are 
carried  on  the  rear  shaft  E  and  are  adjustable.  As  the  shaft 
rotates,  these  fingers  alternately  come  into  contact*  with  spring- 
operated  plungers  which  are  depressed  and  serve  to  withdraw 
a  wedge  from  a  slot  in  a  plate  located  below  the  shifting  device. 
When  the  wedge  is  withdrawn  from  one  slot  in  the  plate,  the 
shifter  is  thrown  so  that  the  wedge  engages  the  next  slot, 
thus  shifting  the  belt  or  belts,  as  the  case  may  be.  There  are 
different  combinations  of  these  shifter  arms  for  various  types 
of  belt  drives. 

Chuck-operating  Mechanism.  —  The  chuck  FI,  Fig.  7,  is 
of  the  push  type  and  is  held  in  the  cap  GI  screwed  onto  the 
nose  of  the  work-spindle.  It  is  operated  by  a  sleeve  HI  that 
receives  motion  from  the  arm  D  (see  also  Fig.  9).  A  detail 
of  this  arm  is  shown  in  Fig.  10,  which  illustrates  its  adjustable 
features.  This  arm  is  provided  with  adjustable  cams  mt  n, 
and  o.  The  cam  m  is  the  chuck-opening  cam,  n  the  safety  cam, 
and  o  the  chuck-closing  cam  which  is  cast  integral  with  the 
arm  D.  Cams  m  and  n  are  on  one  casting  and  are  adjustable 
on  the  arm  D,  being  held  in  the  desired  position  by  three  clamp- 
ing screws  fitting  in  elongated  slots.  There  are  also  additional 
tapped  holes  in  the  arm  allowing  for  further  adjustment. 

When  smooth  stock  is  being  held  in  the  chuck,  the  adjust- 


CLEVELAND   AUTOMATIC 


CLEVELAND   AUTOMATIC 


able  cams  m  and  n  are  set  tightly  up  against  cam  o,  thus  giving 
a  quick  closing  and  opening  action  to  the  chuck  and  allow- 
ing a  short  space  of  time  for  feeding  the  stock.  When  rough 
bar  stock  is  being  handled,  and  for  magazine  work,  it  is  neces- 
sary to  keep  the  chuck  open  much  longer;  for  this  action  the 
cams  m  and  n  are  sepa- 
rated from  cam  o  in  order 
to  allow  additional  time. 
The  action  of  closing 
the  chuck  is  as  follows: 
As  arm  D  rotates,  cam 
m  comes  in  contact  with 
roll  Mi,  Fig.  7,  held  on 
the  fulcrumed  yoke  Ni. 
This  yoke  carries  two 
rolls  that  work  in  a  cir- 
cular groove  cut  in  sleeve 
Oi.  As  the  cam  forces 
this  sleeve  away  from 
the  chuck,  the  sleeve 
acts  upon  two  fingers 

PI  which  bear  against  the  FiS-  10-  Adjustable  Cam  for  Con- 

trolling Operation  of  Chuck 

rear  end  of   the    chuck- 
closing  sleeve  HI.    As  cam  0,  Fig.  10,  comes  into  action,  it 
reverses  the  operation  of  yoke  Oi  and  removes  the  pressure 
from  the  sleeve  Hi,  allowing  the  chuck  to  open,  due  to  spring 
tension. 

Stock-feeding  Mechanism.  —  The  bar  stock  is  fed  through 
the  spindle  by  a  spring  finger  Ji  (Fig.  7)  screwed  into  the  front 
end  of  the  tube  KI,  the  rear  end  of  which  is  provided  with  a 
grooved  collar  LI.  Fitting  in  this  grooved  collar  is  a  forked 
lever  G  which  is  carried  on  the  rod  RI  (Fig.  6).  The  movement 
of  forked  lever  G  is  controlled  by  a  cam  H,  which  contacts 
with  a  roll  held  on  bracket  U\  clamped  to  rod  RI.  Adjust- 
ment for  length  of  feed  is  controlled  by  shifting  the  position 
of  the  bracket  U\  along  rod  RI,  and  the  timing  is  effected  by 
shifting  the  cam  H  around  the  shaft  E.  An  open-wound 


26  SINGLE-SPINDLE  DESIGNS 

coil  spring  serves  to  keep  the  forked  arm  G  and  its  sliding 
bracket  up  against  a  stationary  bracket  when  the  rod  R\  is 
not  acted  upon  by  the  cam.  For  double  feeding,  a  drum  is 
provided  carrying  two  cams,  allowing  for  feeding  the  stock 
twice  for  every  revolution  of  the  camshaft. 

Turret  and  Turret-slide.  —  The  turret  is  of  the  drum  type 
and  is  carried  on  shaft  A2  (Fig.  n)  that  is  parallel  with  the 
work-spindle.  The  turret  on  the  3j-inch  machine  accommo- 
dates six  tools  which  are  held  by  two  clamping  bolts  each,  in 
the  holes  in  the  front  end  of  the  turret,  and  are  located  con- 
centrically with  the  axis  of  the  work-spindle.  The  turret  /  is 
moved  forward  for  cutting  and  backward  for  withdrawing  the 
tools,  by  a  cam-drum  K  which  is  free  to  rotate  on  shaft  A2 
and  carries  segment  cams  B2  fastened  to  its  periphery.  These 
cams  work  against  a  roller  which  is  held  on  a  stud  driven  into 
a  hole  in  the  base  of  the  machine.  As  the  cam-drum  is  rotated 
by  means  of  gearing,  the  engagement  of  the  inclined  cam 
grooves  or  surfaces  with  the  fixed  roller  cause  the  drum  and 
turret  to  move  in  the  direction  of  their  axes,  the  turret  moving 
in  a  straight  line  or  without  rotation,  except  when  indexing. 
Cast  integral  with  drum  K  is  a  spur  gear  D2  which  rotates  it. 
Gear  D2  engages  pinion  E2,  beneath  it,  which,  in  turn,  is  ro- 
tated at  different  speeds  for  the  cutting  and  idle  movements 
of  the  machine  by  a  mechanism  to  be  described  later. 

The  turret  is  indexed  upon  its  back  stroke  by  means  of  a 
rod  H2  held  adjustably  by  locking  nuts  to  a  spur  gear  forming 
part  of  the  feeding  mechanism.  This  rod  comes  into  contact 
with  hardened  pins  held  in  the  rear  face  of  the  turret.  Before 
the  turret  can  be  turned  around,  however,  it  is  necessary  to 
disengage 'a  locking  wedge  from  a  slot  in  the  circumference  of 
the  turret.  This  is  done  by  means  of  a  cam-block  held  on  the 
flange  of  drum  K.  The  indexing  can  be  effected  by  hand  by 
simply  depressing  a  lever,  which  has  the  same  action  on  the 
locking  wedge  as  the  cam-block  held  upon  the  drum  K.  The 
turret  head  is  mounted  on  the  bed  of  the  machine  and  can  be 
adjusted  to  suit  various  lengths  of  work  and  tools  held  in  the 
turret.  The  turret  is  held  to  the  base  of  the  machine  by  means 


CLEVELAND   AUTOMATIC 


28  SINGLE-SPINDLE  DESIGNS 

of  bolts.  A  scale  fastened  to  the  base  of  the  machine  and  a 
pointer  on  the  turret-slide  enable  the  operator  to  obtain  the 
same  setting  of  the  turret  head  when  setting  up  the  machine 
for  a  part  which  has  been  machined  previously. 

Operation  of  the  Cross-slide.  —  On  the  Cleveland  auto- 
matic screw  machine,  as  regularly  equipped,  the  cross-slide 
for  holding  both  the  rear  and  front  cutting  tools  consists  of 
one  casting,  but  a  double  cross-slide  can  be  supplied,  when 
desired.  The  cross-slide  is  actuated  by  means  of  a  fulcrum 
lever  T  (Fig.  n),  which  derives  motion  from  cams  K3  on  the 
drum  U  carried  on  the  rear  shaft  E.  The  flange  of  this  drum 
is  numbered  so  that  the  position  of  the  various  cams  can  be 
recorded  on  a  lay-out  card  to  facilitate  re-setting  the  work. 
The  cross-slide  is  provided  with  an  adjustable  stop-screw 
so  that  accurately  formed  work  can  be  obtained.  It  is  also 
provided  with  adjustable  gibs  to  compensate  for  wear.  The 
position  of  the  cross-slide  relative  to  the  axis  of  the  spindle  is 
controlled  by  regulating  nuts  on  the  connecting-rod  fastened 
to  the  rear  of  the  slide. 

Variable  Feeding  Mechanism.  —  As  the  cam-drum  K 
(Fig.  n)  is  rotated,  the  turret  is  moved  towards  the  spindle 
for  bringing  the  tools  into  contact  with  the  work,  and  then 
backward  for  withdrawing  the  tools.  This  cam-drum  is  ro- 
tated through  gearing  at  a  predetermined  rate  of  speed  which 
is  controlled  by  a  series  of  adjustable  cams  that  automatically 
vary  the  rate  of  the  turret  feeding  movement  according  to  the 
nature  of  the  work.  Motion  for  this  variable  feeding  mecha- 
nism is  derived  from  an  overhead  countershaft  by  a  belt  operat- 
ing on  pulley  N,  which  is  keyed  to  an  extension  of  the  friction 
disk  L.  When  a  fast  movement  is  required,  in  order  to  reduce 
the  non-cutting  or  idle  period  to  a  minimum,  a  sliding  clutch 
is  engaged  with  pulley  N,  so  that  the  drive  is  direct  to  the  worm 
gearing  at  the  rear  of  the  turret,  which  transmits  motion  to 
the  cam-drum  K  through  a  spur  gear,  pinion  E2  and  the 
gear  D%  forming  part  of  the  cam-drum.  This  clutch  is  oper- 
ated by  means  of  levers  that  engage  dogs  F2  which  are  adjust- 
ably mounted  on  the  rear  face  of  the  regulating  drum  £3. 


CLEVELAND  AUTOMATIC  29 

When  the  turret  is  to  be  moved  at  its  slow  or  cutting  speed 
for  feeding  the  tools  forward,  the  clutch  is  shifted  in  the  oppo- 
site direction  by  dogs  Vz  so  that  it  engages  teeth  on  the 
extended  hub  of  a  pinion  which  forms  the  central  member  of 
a  planetary  gear  mechanism.  The  drive  from  belt  pulley  N 
to  the  worm  gearing  at  the  rear  of  the  cam-drum  is  then 
through  friction  disks  L  and  M  and  a  planetary  reduction 
gearing  which  transmits  motion  to  the  worm-shaft  and  is 


Fig.  12.   Detailed  View  of  Automatic  Feed-regulating  Mechanism 

located  adjacent  to  the  worm-wheel,  as  the  illustration  shows. 
This  change  from  fast  to  slow  speed,  or  vice  versa,  can  also  be 
controlled  by  a  handle  at  the  front  of  the  machine. 

The  Feed-regulating  Drum.  —  One  of  the  interesting 
features  of  the  Cleveland  machine  is  the  regulating  drum 
which  is  used  for  securing  independent  feeds  for  each  tool 
in  the  turret  and  on  the  cross-slide.  This  regulation  is  secured 
by  means  of  a  series  of  adjustable  cams  mounted  upon  the 
periphery  of  the  regulating  drum  £3,  Fig.  u.  By  changing 
the  position  of  these  cams,  any  desired  feed  may  be  secured 


30  SINGLE-SPINDLE  DESIGNS 

for  each  tool.  As  each  cam  comes  into  contact  with  lever  Q, 
the  position  of  the  roll  between  friction  disks  L  and  M  is 
changed  with  reference  to  the  center  of  the  disks,  so  that  the 
speed  is  either  increased  or  decreased.  The  bell  crank  lever 
Q  (Fig.  12)  has  a  segment  gear  at  its  outer  end  the  teeth  of 
which  mesh  with  the  sliding  sleeve  R  on  the  rod  Fs.  This 
rod  is  held  in  a  bracket  attached  to  the  machine.  As  sleeve  R 
is  moved  up  and  down  by  the  action  of  lever  Q,  the  position 
of  the  roll  ¥2  between  the  two  friction  disks  is  changed,  thus 
varying  the  speed.  Variations  in  the  position  of  the  friction 
roll  are  transmitted  to  the  pointer  of  the  indicator  dial  Gs, 
so  that  the  positions  of  the  different  regulating  cams  for 
any  given  job  can  readily  be  duplicated,  provided  their  re- 
spective positions,  as  shown  by  the  indicator  dial,  have  been 
properly  recorded.  With  this  arrangement,  a  wide  range  of 
feeds  for  the  turret  and  cross-slide  tools  is  easily  obtained 
and  the  feed  may  also  be  varied  after  the  machine  has  been 
set  up  for  a  given  job,  provided  a  higher  rate  is  considered 
essential  to  economical  production. 

Gridley  Single-spindle  Automatic.  —  The  Gridley  single- 
spindle  automatic  shown  in  Fig.  13  (built  by  the  Windsor 
Machine  Co.)  is  designed  for  handling  straight  bars  of  stock 
up  to  and  including  i\  inches  in  diameter,  and  it  will  feed 
lengths  through  the  chuck  up  to  13!  inches.  These  machines 
are  also  made,  at  the  present  time,  in  two  larger  sizes  for  han- 
dling bars  of  stock  3!  and  4!  inches  in  diameter,  respectively. 
The  spindle  A,  through  which  the  bar  of  stock  is  inserted,  is 
rotated  from  a  parallel  shaft  at  the  rear  to  which  it  is  geared. 
This  rear  driving  shaft  may  either  be  belt-driven  or  motor- 
driven.  The  various  end-working  tools  required  are  attached 
to  slides  B  on  the  turret.  Forming  tools  may  be  held  on  slide 
C  and  a  cutting-off  tool  on  arm  D.  The  movements  of  these 
tools  and  other  parts  of  the  machine  requiring  automatic 
operation  are  controlled  by  cams  mounted  on  the  cam-drums 
E  and  F. 

The  Turret.  —  The  turret  of  the  machine  shown  in  Fig.  13 
does  not  move  axially,  but  it  is  indexed  or  rotated  part  of 


GRIDLEY  AUTOMATIC 


31 


32  SINGLE-SPINDLE  DESIGNS 

a  revolution  after  each  successive  operation  has  been  per- 
formed, in  order  to  locate  the  various  tools  attached  to  it  in 
the  working  position.  The  tool-slides  B  are  given  the  neces- 
sary feeding  movement.  The  axis  of  the  turret  is  parallel 
with  that  of  the  spindle,  but  it  is  lower  than  the  spindle,  so 
that  the  tools  attached  to  the  different  slides  of  the  turret 
will  be  in  alignment  with  the  spindle  when  indexed  to  the 
upper  position.  This  turret  revolves  in  bearings  located  in 
both  ends  of  the  main  frame  or  headstock  of  the  machine. 
The  turret  is  revolved  by  a  worm  which  has  an  intermittent 
movement  and  engages  a  worm-wheel  located  between  the 
turret  bearings.  The  machine  can  be  so  adjusted  that  the 
turret  stops  only  at  the  tool  positions  required  and  skips  any 
of  the  regular  locations,  if  it  is  not  necessary  to  use  all  of  the 
tool-slides. 

The  turret  is  rigidly  held  in  its  different  positions  by  a  locking 
pin  which  engages  steel  plates  set  in  the  periphery  of  a  locking 
disk  attached  to  the  turret. 

Tool-slides  on  Turret. — The  slides  which  hold  the  end- 
working  tools  are  gibbed  to  the  square  end  of  the  turret  cast- 
ing that  extends  beyond  the  frame  of  the  machine.  These 
slides  are  moved  toward  and  away  from  the  chuck  by  suit- 
able cams  attached  to  the  cam-drum  E.  The  longitudinal 
movement  is  transmitted  from  the  feed  cam-drum  to  whatever 
tool-slide  is  in  the  working  position,  by  means  of  draw-bar 
G  (Fig.  14)  which  extends  through  the  center  of  the  turret 
and  has  a  roll  for  engaging  the  cam  on  one  end  and  is  con- 
nected to  a  tool-slide  at  the  other.  When  a  tool-slide  comes 
around  to  the  working  position,  a  pin  P,  attached  to  the  slide, 
engages  a  notch  in  a  collar  attached  to  shaft  G.  When  the 
turret  indexes,  this  pin  moves  out  of  the  notch  and  the  pin  on 
the  next  successive  tool-slide  enters  the  notch. 

The  tool-slides  are  provided  with  T-slots  throughout  their 
length,  so  that  the  tool-holders  can  be  secured  to  them  at 
any  point,  or  several  tools  may  be  attached  to  the  same  slide, 
if  necessary,  one  being  back  of  the  other.  Between  the  tool- 
slides  or  at  the  corners  of  the  turret,  accessories  to  the  tools 


GRIDLEY  AUTOMATIC 


33 


may  be  applied,  such  as  drill-supports,  stops  for  self-opening 
dies,  taper  guides,  etc.,  or  a  stop  for  the  stock  when  all  of  the 
tool-slides  are  required  for  tools.  This  method  of  mounting 
the  tools  on  slides  enables  each  tool  to  be  given  a  rigid  support. 
Operation  of  Forming  and  Cutting-off  Tools.  —  The  forming 
slide  C  at  the  front  of  the  machine,  and  the  cutting-off  tool 
held  by  the  swinging  arm  D  at  the  rear,  are  operated  inde- 
pendently of  each  other.  As  the  back-rests  in  the  turners 
held  on  the  turret  are  so  located  as  to  take  the  thrust  of  the 


Machinery 


Fig.  14.   Sectional  View  showing  Method  of  Supporting  Turret  and  Operating 

Tool-slides 

forming  tool,  turning  and  forming  operations  can  be  performed 
at  the  same  time,  or  the  turner  may  be  used  as  a  support  for 
the  work  when  the  forming  tool  is  in  action. 

Arrangement  of  Cams.  —  The  camshaft  carries  the  feed 
cam-drum  E  and  the  operating  cam-drum  F.  The  cam  H  on 
drum  £,  through  the  medium  of  draw-bar  G  extending  through 
the  machine,  imparts  a  forward  feeding  movement  to  the  tool- 
slides;  cam  /  controls  the  return  movement.  Three  feed 
cams  are  regularly  furnished  with  the  machine.  The  inclina- 
tion of  these  cams  vary  so  that  they  give  fine,  medium,  and 
coarse  feeds;  they  may  readily  be  located  anywhere  on  the 


34 


SINGLE-SPINDLE   DESIGNS 


CHICAGO  AUTOMATIC  35 

cam-drum,  as  they  are  held  in  position  by  two  cap-screws. 
The  camshaft  has  a  rapid  and  a  slow  movement.  The  cams 
for  operating  the  high-speed  lever  K  which  controls  the  rapid 
and  slow  movements  of  the  camshaft  are  held  in  a  circular 
T-slot  in  the  left-hand  edge  of  the  operating  cam-drum  F. 
A  set  of  cams  L,  for  operating  the  belt  shippers,  is  also  at- 
tached to  this  cam-drum.  The  dogs  for  operating  the  turret- 
revolving  mechanism  at  the  proper  time  are  held  in  a  circular 
T-slot  extending  around  the  right-hand  edge  of  cam-drum  F. 
The  cams  for  operating  the  forming  slide  C  and  the  cutting-off 
arm  D  are  attached  to  disk  M.  The  forming-slide  cam  is  lo- 
cated on  one  side  of  the  disk  and  the  cutting-off  cam  on  the 
other  side.  These  cams  are  held  in  place  by  screws,  so  that 
they  can  readily  be  changed.  The  cams  for  opening  and  clos- 
ing the  spindle  chuck  are  located  at  N,  and  the  movement  for 
feeding  the  stock  through  the  spindle  is  derived  from  cam  0. 

Application  of  Motor  Drive.  —  When  the  Gridley  automatic 
is  motor-driven,  two  variable-speed  motors  are  employed, 
each  having  its  own  controller,  resistance,  etc.  One  motor 
drives  the  spindle  while  the  other  drives  the  feeding  mecha- 
nism, so  that  the  cutting  speed  and  the  feed  are  independently 
controlled.  The  feed  or  speed  may  be  varied  automatically 
as  the  controllers  for  each  motor  are  operated  by  cams  on  the 
operating  cam-drum. 

The  Chicago  Automatic  Screw  Machine.  —  The  single- 
spindle  automatic  screw  machine  shown  in  Fig.  15  (built  by 
the  Chicago  Automatic  Machine  Co.)  is  driven  by  a  single 
belt  from  the  lineshafting  direct  to  tight  and  loose  pulleys  at 
M  on  the  rear  shaft  of  the  machine.  The  lever  R  controls 
the  position  of  the  belt.  The  shaft  on  which  the  pulleys  are 
mounted  drives  the  main  drive  shaft  N  through  two  change- 
gears,  which  are  enclosed  in  the  case  on  the  left-hand  end  of 
the  machine.  The  work-spindle  is  driven  from  this  main  drive 
shaft  through  gearing  having  a  ratio  of  5  to  8,  and  these  gears 
are  never  changed.  The  main  drive  shaft  extends  the  entire 
length  of  the  machine  and  through  gearing,  drives  the  mecha- 
nism for  rotating  and  indexing  the  turret,  operating  the  cam- 


36  SINGLE-SPINDLE  DESIGNS 

shaft,  and,  through  a  separate  spindle  and  gear,  the  threading 
mechanism. 

Chuck  Feeding  Mechanism.  —  The  spindle  of  the  machine 
is  provided  with  the  usual  spring  chuck  and  friction  feeding 
finger.  This  mechanism  is  operated  by  cams  on  drum  A. 
Segment  B  pulls  the  feeding  tube  back  and,  when  the  chuck 
is  opened  by  the  segment  C,  the  spring  D  forces  the  stock  for- 
ward against  the  stop.  The  chuck  is  then  closed  by  the  regular 
type  of  chuck-closing  fingers.  In  setting-up  the  machine  on 
a  new  job,  considerable  saving  in  stock  can  be  effected  by  pull- 
ing lever  E  up.  This  removes  roll  F  from  the  path  of  the  seg- 
ment and  prevents  the  chuck  from  opening  and  the  stock  from 
feeding.  This  enables  the  operator  to  set-up  all  the  tools  on 
one  piece  without  spoiling  a  large  number  of  parts  before  the 
required  size  and  shape  is  obtained. 

Turret  Mechanism.  —  The  turret  J  derives  its  indexing 
movement  from  the  main  drive  shaft  N  through  a  train  of 
gears  and  a  friction  clutch,  which  is  operated  at  the  proper 
time  by  circular  segments  or  cams  attached  to  the  rear  side  of 
index  plate  P.  These  segments  control  the  engagement  of 
the  friction  clutch  when  the  turret  has  been  withdrawn  and, 
in  this  way,  the  turret  is  rotated  far  enough  to  locate  the  next 
successive  tool  opposite  the  work-spindle.  In  many  cases, 
tools  are  not  needed  in  some  of  the  holes  in  the  turret  and 
these  empty  holes  can  be  skipped  in  indexing,  by  attaching 
long  circular  segments  to  the  side  of  the  index  plate.  If  only 
two  tools  were  used,  there  should  be  two  long  circular  segments 
on  the  index  plate,  whereas,  if  three  tools  were  used,  there 
should  be  two  short  segments  and  one  long  one,  and  so  on. 
After  the  turret  is  approximately  located  by  the  indexing 
mechanism,  it  is  accurately  aligned  by  a  guide  which  engages 
the  notches  in  the  index  plate  P  when  the  turret  is  advanced 
to  the  working  position.  When  setting-up  the  machine,  the 
turret  can  readily  be  indexed  by  means  of  lever  H  which  serves 
to  engage  the  clutch  at  the  rear  of  the  machine. 

The  Camshaft.  —  The  camshaft  is  driven  from  shaft  N 
through  a  train  of  gears  at  the  right-hand  end  of  the  machine, 


CHICAGO  AUTOMATIC  37 

these  gears  being  changed  in  accordance  with  the  speed  re- 
quired as  determined  by  the  number  of  spindle  revolutions 
necessary  to  complete  a  series  of  operations.  There  are  fifty 
divisions  around  the  circumference  of  the  cam,  marked  by  rows 
of  tapped  holes  one  inch  apart,  so  that  the  circumference  of 
the  cam  is  50  inches.  In  order  to  illustrate  how  the  lengths  of 
the  cams  for  the  different  tools  are  determined,  assume  that 
a  piece  requires  a  milling  operation  for  a  length  of  one  inch. 
With  a  feed  of  0.005  inch,  this  will  require  about  200  revolu- 
tions (i  -r-  0.005  =  200)  and,  in  the  same  way,  the  number 
of  spindle  revolutions  for  the  other  operations  is  obtained. 
If  the  total  number  for  a  complete  series  of  operations  were, 
say,  1040,  this  number  divided  by  50  (number  of  divisions  on 
the  cam)  equals  approximately  21,  which  represents  the  num- 
ber of  spindle  revolutions  for  every  inch  on  the  cam  circum- 
ference. By  dividing  the  number  of  spindle  revolutions  for 
the  milling  operation,  or  200  by  21,  the  result  equals  the  length 
of  the  segment  on  the  cam  for  this  particular  operation;  thus 
200  -T-  21  =  9!  inches,  approximately.  As  the  cut  is  to  be  one 
inch  long,  the  segment  should  have  a  lead  or  rise  of  about  lyV 
inch.  The  lengths  of  other  segments  for  different  operations 
can  be  determined  in  the  same  way.  The  return  segments 
for  the  turret  are  always  the  same,  although  their  position  may 
have  to  be  changed  for  different  operations. 

The  Cross-slides.  —  The  cross-slides  of  the  machine  shown 
in  Fig.  15  are  operated  independently  by  plates  or  cams  at- 
tached to  drum  K.  These  cams  impart  motion  to  the  cross- 
slides  through  fulcrumed  levers  which  are  connected  at  their 
lower  ends  by  means  of  a  spring  L  that  keeps  the  rolls  in  con- 
tact with  the  cams.  These  cams  for  controlling  the  movements 
of  the  forming  and  cutting-off  tools  do  not  require  much 
adjustment,  although  sometimes  a  longer  or  shorter  cam  is 
required.  The  cross-slides  are  provided  with  adjusting  screws 
for  setting  the  tools  in  the  correct  position  relative  to  the 
work. 

Method  of  Cutting  Threads.  —  For  threading  operations, 
a  central  spindle  is  used,  which  is  driven  directly  by  gearing. 


38  SINGLE-SPINDLE  DESIGNS 

On  the  i^-inch  machine,  this  gearing  is  so  arranged  that,  for 
every  100  revolutions  of  the  spindle,  the  tap  or  die  will  make 
128  revolutions,  so  that  28  threads  will  be  cut  irrespective  of 
the  pitch  of  the  thread  for  every  100  revolutions  of  the  spindle. 
If  the  spindle  makes  50  revolutions,  14  threads  will  be  cut,  or 
7  threads  for  every  25  revolutions  of  the  spindle.  As  the 
spindle  always  runs  backwards,  and  since  the  threading  die 
runs  faster  than  the  spindle,  it  is  evident  that  the  variation 
in  speed  is  utilized  for  cutting  the  thread.  Whenever  a  thread 
has  been  cut  to  the  required  length  and  the  turret  starts  to 
withdraw  the  die,  the  driving  pins  of  the  die-holder  are  dis- 
engaged and  then  the  die-holder  is  held  stationary  by  the 
engagement  of  a  clutch,  thus  backing  the  die  off  of  the  thread. 

Feeding  Movements  for  Tools.  —  The  feeds  recommended 
for  ordinary  work  on  this  machine  are  as  follows:  When 
turning  machine  steel  with  box-tools,  the  feed  may  vary 
from  0.004  to  o.oio  inch  for  roughing,  and,  for  finishing,  from 
0.002  to  0.006  inch  per  revolution  of  the  work.  For  drills  less 
than  |  inch  in  diameter,  the  feeds  may  vary  from  0.002  to  0.006 
inch,  and,  for  drills  over  f  inch  in  diameter,  from  0.006  to  0.015 
inch  per  revolution.  For  forming  tools,  the  feeds  may  vary 
from  0.00025  to  0.004  inch,  the  amount  depending  upon 
the  width  of  the  forming  tool  and  the  diameter  of  the  stock 
being  formed.  Cut  ting-off  tools  may  be  given  a  feed  of  from 
0.002  to  0.004  inch  per  revolution.  When  operating  on  brass 
stock,  the  feeds  previously  given  may  be  doubled. 


CHAPTER  III 
MULTIPLE-SPINDLE   AUTOMATIC    SCREW    MACHINES 

THE  multiple-spindle  screw  machine  represents  a  develop- 
ment of  the  single-spindle  type  and  was  designed  primarily 
to  increase  production,  by  grouping  several  work-spindles 
together  so  that  separate  bars  of  stock  —  one  in  each  spindle 
-  could  be  operated  upon  simultaneously.  With  this  ar- 
rangement, when  there  are  several  end-working  tools,  such  as 
a  box-tool,  a  drill,  a  reamer,  and  a  threading  die,  all  of  these 
tools  operate  on  different  bars  of  stock  as  the  turret  moves 
forward,  instead  of  indexing  first  one  tool  and  then  another  to 
the  working  position,  as  is  necessary  when  all  the  operations 
are  performed  successively  upon  the  end  of  a  single  bar  of  stock. 
The  advantage  of  the  multiple-operation  method,  as  previ- 
ously explained,  is  that  the  time  required  for  producing  a  part 
is  equivalent  to  the  longest  single  machining  operation  plus 
the  non-cutting  period  necessary  for  advancing  the  tools  to 
the  work,  withdrawing  them,  and  indexing  the  spindle  carrier, 
whereas,  with  a  single-spindle  machine,  the  production  time 
equals  the  total  time  for  all  of  the  operations  plus  the  idle  or 
non-cutting  period. 

Acme  Automatic  Screw  Machine.  —  The  National- Acme 
automatic  multiple-spindle  screw  machine  shown  in  Fig.  i 
illustrates  the  general  principle  governing  the  construction 
and  operation  of  screw  machines  of  this  class.  The  machine 
has  four  parallel  work-spindles  At  which  are  equally  spaced 
and  equidistant  from  the  axis  of  the  cylindrical  head  in  which 
the  spindles  are  mounted.  Each  spindle  contains  a  bar  of 
stock  when  the  machine  is  in  operation,  and  the  bar,  as  it 
rotates  with  the  spindle,  is  operated  upon  by  tools  held  in 
an  opposing  tool-slide  B  and  also  upon  cross-  or  side-working 
tool-slides  C.  A  tool  from  the  side  and  one  from  the  end  may 

39 


MULTIPLE-SPINDLE   DESIGNS 


NATIONAL- ACME  SCREW  MACHINE  41 

work  together  on  each  bar,  and  all  of  the  tools  engage  the  stock 
at  practically  the  same  time. 

When  the  tools  are  all  withdrawn,  the  cylinder  contain- 
ing the  work-spindle  is  indexed  or  revolved  far  enough  to 
locate  each  spindle  opposite  the  next  successive  set  of  tools 
which  perform  additional  operations.  When  each  bar  reaches 
the  last  tool  or  set  of  tools  in  the  series,  the  completed  part  is 
severed  from  the  bar,  which  is  then  automatically  moved  out- 
ward through  the  spindle  far  enough  for  turning  another  piece. 
With  this  arrangement,  a  part  is  finished  each  time  the  spindle 
head  indexes  one-quarter  of  a  revolution. 

Order  of  Operations.  —  With  the  machine  illustrated  in 
Fig.  i,  there  are  eight  standard  tool  positions,  four  being 
from  the  side  and  four  from  the  end,  thus  allowing  eight  inde- 
pendent tools  to  be  used,  if  necessary.  The  stop  which  engages 
the  feeding  movement  of  the  stock  does  not  occupy  a  tool 
position.  Assuming  that  eight  operations  were  required,  the 
sequence  or  order  in  which  the  various  tools  are  presented  to 
the  work  would  be  about  as  follows : 

After  the  preceding  piece  is  cut  off  in  the  fourth  position, 
a  new  length  of  stock  is  fed  forward,  the  feeding  movement 
occurring  during  the  indexing  from  the  fourth  to  the  first 
position,  or  with  the  larger  type  of  machine  in  the  fourth 
position,  as  the  indexing  is  being  completed.  The  cams  next 
bring  forward  one  tool  from  the  side  (usually  a  forming  tool) 
and  also  a  tool  from  the  end,  which  may  be  a  box-tool,  drill, 
or  tool  for  facing,  countersinking,  etc.  The  bar  is  then  in- 
dexed to  the  second  position,  where  it  may  be  operated  upon 
by  a  shaving  tool  in  the  front  top  slide,  or  tools  for  light  form- 
ing, knurling,  or  thread  rolling;  at  the  same  time,  tools  in 
the  main  slide  may  be  used  for  milling,  drilling,  reaming, 
countersinking,  facing,  etc.  The  bar  is  next  indexed  to  the 
third  position,  or  opposite  the  rear  top  slide,  which  may  carry 
a  knurling  tool,  a  thread-rolling  tool,  or  one  for  a  forming 
or  shaving  operation.  The  end  tool  may  drill,  ream,  counter- 
bore,  tap  a  hole,  or  cut  an  external  thread.  In  addition,  at- 
tachments are  frequently  used  in  this  third  position  for  milling 


Fig.  2.   Spindle-driving  and  Stock-feeding  Mechanism 


Fig.  3.   Main  Tool-slide  and  End-working  Tool-holding  Spindles 


NATIONAL-ACME   SCREW  MACHINE  43 

from  the  end,  and  for  drilling  from  the  side  or  milling  from  the 
side,  etc.  The  use  of  these  attachments  is  made  possible  be- 
cause the  work-spindle  can  be  stopped  in  this  position.  In 
the  fourth  position,  opposite  the  rear  horizontal  slide,  the 
end  tools  may  countersink,  counterbore,  drill,  etc.,  whereas 
the  cross-slide  may  be  used  for  finish-forming,  after  which 
the  finished  part  is  severed  from  the  bar. 

The  operations  previously  referred  to  merely  indicate, 
in  a  general  way,  how  the  tool  equipment  may  be  used.  The 
order  of  the  operations  and  the  tools  used  depend  upon  the 
conditions  governing  each  case.  For  instance,  knurling  can 
be  done  in  the  first  and  fourth  positions  from  the  side,  if  neces- 
sary, or  from  any  of  the  end  positions.  Threading  can  some- 
times be  done  in  the  second  position.  Moreover,  threads  can 
be  rolled  in  the  fourth  position,  if  necessary,  the  order  being 
varied  according  to  the  requirements  of  the  work. 

Spindle-driving  Mechanism.  —  The  four  work-spindles  of 
the  machine  shown  in  Fig.  i  are  driven  by  gears  meshing 
with  a  central  gear  on  the  driving  shaft  D  which  derives  its 
motion  from  the  belt  pulley  E  and  extends  through  the  main 
tool-slide  and  spindle  head  to  the  central  driving  gear.  These 
spindle  gears  are  not  attached  directly  to  the  spindles  but  are 
driven  through  friction  clutches  which  permit  each  spindle 
to  be  stopped  at  the  third  position  in  case  a  threading  opera- 
tion is  necessary.  The  exact  arrangement  of  the  spindle- 
driving  mechanism  is  shown  more  clearly  in  the  detail  view, 
Fig.  2.  In  this  illustration,  the  shaft  HI  corresponds  to  the 
main  driving  shaft  D  in  Fig.  i.  The  spur  gears  /i,  which  are 
driven  from  the  central  shaft,  are  free  to  rotate  on  bronze 
bushings  and  are  provided  with  taper  projections  or  shoulders 
which  form  the  internal  member  of  a  friction  driving  clutch. 
The  other  member  of  this  driving  clutch  consists  of  a  tapering 
cup  KI,  which  is  keyed  to  a  sleeve  that  is  keyed  to  the  spindle. 
The  cup  is  held  into  engagement  with  the  friction  gear  I\ 
by  coil  springs  L3.  The  way  in  which  these  friction  clutches 
are  utilized  in  connection  with  threading  operations  will  be 
described  later. 


44 


MULTIPLE-SPINDLE   DESIGNS 


The  Camshaft.  —  There  is  only  one  camshaft  on  the 
machine  illustrated  in  Fig.  i,  and  this  is  under  the  bed  and 
carries  all  of  the  operating  cams  for  controlling  the  move- 
ments of  the  various  slides,  and  also  a  segment  gear  for 
indexing  the  spindle  head.  This  shaft  carries  the  two  main 


Machinery 


Fig.  4.   End  View  of  Machine  showing  Speed-changing  Mechanism  for 
Camshaft 

cam-drums  F  and  G.  Attached  to  drum  F  are  the  cams  for 
operating  the  stock-feeding,  chuck-closing,  and  opening  mecha- 
nisms, and  also  the  dogs  for  operating  the  friction  clutches 
which  engage  or  disengage  the  work-spindles  from  their  driving 
gears.  On  drum  G  are  cams  for  operating  the  main  tool-slide, 
and,  on  some  machines,  a  thread-starting  mechanism.  This 
camshaft  makes  four  complete  revolutions  to  one  revolution  of 


NATIONAL-ACME  SCREW  MACHINE  45 

the  spindle  head,  and  a  complete  range  of  speeds  is  provided 
by  means  of  change-gears. 

Camshaft  Speed-changing  Mechanism.  —  The  upper  or 
main  driving  shaft  D,  Fig.  i,  which  drives  the  four  work- 
spindles  of  the  machine,  transmits  motion  to  the  camshaft 
beneath  the  bed  through  the  mechanism  illustrated  in  Fig.  4, 
which  enables  the  camshaft  to  be  rotated  at  a  suitable  speed. 
The  pulley  U$  (which  corresponds  to  pulley  E,  Fig.  i)  is  driven 
from  a  constant-speed  countershaft.  This  pulley  normally 
runs  free  on  the  driving  shaft,  but  can  be  secured  to  it  for 
driving  direct  when  necessary.  Attached  to  the  inner  hub  of 
this  belt  pulley,  there  is  a  bevel  gear  V5)  which  meshes  with 
another  bevel  gear  on  the  shaft  W^  which  transmits  motion 
to  the  horizontal  shaft  ¥5  through  additional  bevel  gearing. 
(On  some  of  these  machines,  spiral  gears  are  used  instead  of 
bevel  gears.)  From  this  point,  motion  is  transmitted  to  the 
camshaft  by  means  of  change  gearing,  which  is  selected  in 
accordance  with  the  speed  required.  The  sleeve  A6  of  this 
clutch  is  keyed  to  the  horizontal  shaft  ¥5,  and  sleeve  B& 
passes  through  the  bearing  in  the  frame  and  forms  a  part  of 
a  sprocket  and  clutch  at  C&.  The  shaft  F5  is  also  continued 
through  the  frame  and  has  a  washer  E$  keyed  to  its  outer 
end.  , 

The  first  gear  of  the  four  change-gears  is  keyed  to  this 
washer  and  meshes  with  a  larger  gear  on  the  stud.  The  mo- 
tion is  then  transmitted  through  two  other  gears  to  a  clutch 
of  which  the  sprocket  C6  forms  a  part.  Motion  is  further 
transmitted  to  the  camshaft,  when  the  tools  are  at  work, 
by  means  of  a  chain  which  drives  another  sprocket  that  is 
connected  to  a  worm-shaft.  This  worm-shaft,  in  turn,  drives 
a  worm-wheel  which  is  mounted  upon  the  right-hand  end  of 
the  camshaft  of  the  machine  as  shown  in  Fig.  i.  The  sprocket 
on  the  worm-shaft  may  be  disengaged  from  the  shaft  by  means 
of  a  clutch  controlled  by  a  hand  lever.  The  sprocket  is  pro- 
vided with  a  safety  device  in  the  form  of  two  fiber  collars 
which  are  kept  into  frictional  contact  by  a  nut.  This  nut  is 
tightened  sufficiently  to  drive  the  worm-shaft  when  the  ma- 


46 


MULTIPLE-SPINDLE  DESIGNS 


chine  is  operating  under  normal  conditions,  but,  in  case  of 
unusual  strain,  slippage  occurs,  thus  relieving  the  gearing  and 
other  parts  of  the  machine. 

For  the  idle  movements  of  the  machine  or  those  movements 
which  occur  when  the  tools  are  not  in  operation,  as  when  feed- 
ing the  stock,  indexing  the  cylinder,  and  moving  the  tools  to 
and  from  the  work,  the  camshaft  is  driven  at  the  "direct 


SHAFT 


Machinery 


Fig.  5.   Gears  used  in  Obtaining  Changes  of  Spindle  Speed 

speed"  which  is  much  faster  than  the  regular  cutting  speed, 
in  order  to  reduce  the  idle  period  to  a  minimum.  This  direct 
drive  is  obtained  by  shifting  the  sleeve  A&  to  the  left,  so  that 
motion  is  transmitted  to  the  sprocket  C6  direct  from  shaft  Y5) 
instead  of  through  the  combination  of  change  gearing.  The 
change  of  speed  from  the  direct  to  the  cutting  speed,  and 
vice  versa,  is  controlled  automatically  by  dogs  on  a  cam-drum 
located  at  the  right-hand  end  of  the  camshaft.  This  cam 


NATIONAL-ACME  SCREW  MACHINE  47 

transmits  motion  through  suitable  shafts  and  levers  to  the 
sliding  member  A6  of  the  friction  clutch.  The  method  of 
determining  the  change-gears  to  use  in  any  case  is  explained 
in  Chapter  V,  which  deals  with  the  adjustment  and  setting-up 
of  screw  machines. 

Speed  of  Main  Driving  Shaft.  —  The  speed  of  the  main 
driving  shaft  from  which  all  other  members  of  the  machine 
are  driven  can  be  varied  by  means  of  the  gearing  shown  in 
Fig.  5.  The  direct  speed  is  obtained  by  first  sliding  the  gears 
A  and  B  out  of  contact  with  gear  C  on  the  shaft,  and  the 
gear  D  which  is  attached  to  the  hub  of  the  belt  pulley  U$, 
or  by  removing  the  gears  A  and  B  entirely.  Then  a  sleeve 
that  is  keyed  on  the  end  of  the  main  driving  shaft  is  fastened 
to  the  belt  pulley  by  screws.  In  order  to  change  from  the 
direct  drive  to  the  drive  through  the  back-gears,  the  screws 
binding  the  sleeve  to  the  pulley  are  removed  and  motion  is 
transmitted  through  gears  A,  B,  C,  and  Z>,  which  are  selected 
in  accordance  with  the  speed  required  and  as  shown  by  a  table 
accompanying  the  machine. 

Main  Tool-slide.  —  The  main  tool-slide  B  (Fig.  i)  carries 
the  end-working  tools  and  also  the  driving  mechanism  for  the 
threading  spindle,  as  well  as  the  cams  which  control  the  move- 
ments of  the  two  top  slides  C.  The  main  slide  is  actuated  by 
cams  directly  beneath  it  which  engage  a  roll  attached  to  the 
under  side.  These  cams  are  set  so  as  to  bring  the  tools  up  to 
the  work  quickly,  feed  them  while  cutting,  at  a  comparatively 
slow  speed,  and  then  withdraw  the  tools  at  a  higher  rate  of 
speed.  As  the  roll  travels  over  these  " fast-angle"  cams,  the 
speed  of  the  camshaft  is  increased  considerably,  and  then 
reduced  to  the  cutting  speed  as  soon  as  the  tools  are  in  the 
working  position. 

A  detail  view  of  the  main  tool-slide  is  shown  in  Fig.  3, 
where  it  is  represented  by  the  reference  letter  M%.  There  are 
four  tool  spindles  to  correspond  to  the  four  work-spindles  of 
the  machine.  The  spindle  Nz  is  in  what  is  known  as  the 
"first"  position;  02,  in  the  "second"  position;  P2,  in  the 
"third";  and  Q2,  in  the  " fourth"  position.  The  tool  spindles 


48  MULTIPLE-SPINDLE   DESIGNS 

N2  and  Q2  are  held  stationary  in  the  main  tool-slide,  whereas 
the  spindles  02  and  P2  may  be  revolved.  The  spindle  P2 
is  the  one  used  for  threading  operations,  as  will  be  described 
later.  The  spindle  O2  is  rotated  when  it  is  necessary  to  drill 
a  small  hole  in  a  comparatively  large  piece  of  work.  Without 
this  feature  the  speed  of  the  work-spindle  would  have  to  be 


Fig.  6.   Main  Tool-slide  removed,  showing  Arrangement  of  the  Cross-slides  on  the 
"Acme"  Multiple-spindle  Automatic  Screw  Machine 

increased  considerably  in  order  to  drill  a  small  hole  efficiently. 
This  tool-spindle  is  also  used  for  holding  a  threading  tool, 
if  necessary. 

Operation  of  the  Cross-slides.  —  The  lower  horizontal  cross- 
slides  shown  at  £5  and  F&  in  the  detailed  view,  Fig.  6,  carry 
the  forming  and  cutting-off  tools  and  are  moved  toward  and 
away  from  the  work  by  levers,  the  lower  ends  of  which  are 
engaged  by  cams  on  the  disk  K,  Fig.  i.  These  two  slides  are 


NATIONAL-ACME   SCREW  MACHINE  49 

mounted  on  auxiliary  slides  G$  and  #5,  which  are  adjustable 
along  the  bed  of  the  machine,  which  adjustment  permits  chang- 
ing the  positions  of  the  forming  and  cutting-off  tools  relative 
to  the  work,  without  adjusting  the  tools  in  the  tool-holders. 
The  upper  ends  of  the  levers  which  operate  these  slides  engage 
slots  on  the  under  sides  of  the  slides,  and  the  lower  ends  are 
provided  with  rollers  which  come  into  contact  with  the  cam- 
shoes.  On  some  of  the  Acme  machines,  these  operating  levers 
are  drilled  in  two  separate  places  for  the  pins  upon  which  they 
swing.  This  feature  makes  it  possible  to  form  deeper  and  cut 
off  larger  diameters  of  stock,  when  the  levers  are  pivoted  in 
the  lower  holes,  without  using  cams  of  greater  throw.  The 
forming  slide  E5  is  provided  with  a  stop  and  an  adjustable 
stop-screw,  to  check  it  at  the  end  of  the  cam  movement  so 
that  duplicate  parts  may  be  turned  to  the  same  diameter. 

The  upper  cross-slides  P5  and  ()5  for  operating  in  the  second 
and  third  positions,  respectively,  are  similar  in  construction 
to  the  lower  slides,  but  are  operated  by  strip  cams  which  are 
attached  to  and  receive  their  motion  from  the  main  tool- 
slide,  as  shown  in  Fig.  3.  The  angles  of  these  strip  cams  are 
governed  by  the  rate  of  feed  desired  and  the  lead  of  the  cam 
operating  the  main  tool-slide.  The  slide  P&  in  Fig.  6  is  equipped 
with  a  shaving  tool,  whereas  the  slide  Qb  has  a  knurling  tool. 

Indexing  Mechanism.  —  The  head  in  which  the  four  spin- 
dles is  mounted  is  indexed  a  quarter  turn  between  the  suc- 
cessive machining  operations,  by  means  of  a  segment  gear  H, 
Fig.  i,  which  engages  teeth  at  the  rear  end  of  the  spindle  head. 
This  segment  or  fan  gear,  which  is  shown  more  clearly  at  J 
in  Fig.  7,  is  mounted  on  the  main  camshaft  M  of  the  machine, 
which,  as  previously  mentioned,  makes  four  revolutions  to 
one  complete  turn  of  the  cylinder.  Provision  for  accurate 
alignment  of  the  spindles  with  the  tools  in  the  tool-slide  is 
made  by  means  of  two  plungers  O  and  K.  The  plunger  0 
drops  into  position  first  and  is  brought  into  contact  with  the 
aligning  screw  N;  then  the  other  plunger  K  is  forced  in  against 
a  hardened  steel  taper  plug.  The  bolt  K  is  withdrawn  by  an 
arm  P  fulcrumed  at  O  and  operated  by  a  dog  R  on  the  cam- 


MULTIPLE-SPINDLE  DESIGNS 


shaft.  This  dog  should  engage  fully  with  the  end  of  the  arm 
before  the  first  tooth  of  the  segment  gear  J  comes  into  contact 
with  the  cylinder.  In  operation,  as  the  bolt  K  is  withdrawn, 
the  first  tooth  in  the  segment  gear  J  comes  into  contact  with 
the  cylinder,  thus  rotating  it  and,  at  the  same  time,  forcing 
back  the  bolt  O.  Then,  as  the  cylinder  revolves  around  to  the 


Machinery 


Fig.  7.   View  showing  how  the  Cylinder  is  indexed  and  locked  in  Position 

next  position,  the  bolt  0  is  forced  into  the  cavity  in  front  of 
the  aligning  screw  N  by  a  coil  spring.  As  the  arm  drops  off 
of  the  dog  T,  the  bolt  K  is  forced  home  by  the  coil  spring  V, 
thus  drawing  the  cylinder  back  and  seating  the  aligning  screw 
^V  firmly  on  the  flat  part  of  the  bolt  0. 

Operation  of  the  Spindle  Chuck.  —  The  opening  and  closing 
of  each  spindle  chuck  at  the  point  where  the  stock  must  be 


NATIONAL-ACME   SCREW  MACHINE  51 

moved  forward  is  controlled  by  a  cam  Vi,  on  drum  W\,  Fig.  2, 
which  actuates  lever  Ui  connecting  with  whatever  sleeve  on 
the  spindle  is  in  the  stock-feeding  position.  (The  drum  Wi 
and  lever  U\  correspond  with  drum  F  and  lever  I,  Fig.  i.) 
The  spring  chucks  are  of  the  push  type  and  are  forced  forward 
for  tightening,  whenever  a  tapered  collar  TI  is  pushed  back- 
ward by  the  lever  U\.  The  tapered  collars  T\  actuate  the 
steel  sleeves  Oi  by  means  of  the  levers  PI  which  are  forced 
outward  in  the  usual  manner.  In  order  to  tighten  the  spring 
chucks  on  the  bars  of  stock,  hollow  set-screws  in  the  collar  S\ 
should  first  be  unscrewed  and  then  the  collars  are  turned  to  the 
right,  which  changes  the  fulcrum  point  of  the  chuck  operat- 
ing levers. 

Feeding  the  Stock  through  the  Spindle.  —  The  lever  for 
operating  the  stock-feeding  tube  also  derives  its  motion  from 
a  cam  on  the  drum  Wit  Fig.  2.  This  lever  D2  is  pivoted  at 
its  lower  end  and  connects  with  a  cam  on  the  drum  by  means 
of  lever  E2  and  rod  F2.  The  length  of  the  feeding  movement 
is  controlled  by  adjusting  the  stop  G2  on  the  rod  F2,  thus  vary- 
ing the  distance  that  the  rod  F2  travels  through  lever  D2 
before  moving  it.  The  stock  is  fed  against  a  stop  or  gage,  and, 
on  the  smaller  machines,  the  feeding  is  done  during  the  index- 
ing, the  stop  being  located  between  the  fourth  and  first  tool 
positions.  On  the  larger  machines,  a  cam  control  brings  the 
stop  into  the  first  position  and  withdraws  it  after  the  stock  is 
fed  against  it  and  before  the  tools  feed  up  to  the  work.  The 
feed-tube  B2  is  first  withdrawn  by  lever  D2,  causing  the  feed 
finger  A2  to  slide  over  the  bar  which  is  held  tightly  in  a  spring 
chuck  NI.  Cam  lever  U\  next  releases  the  chuck,  and  feed- 
tube  B2  is  pushed  forward.  As  the  forward  movement  begins, 
the  feed  finger  A2  grips  the  stock  and  forces  the  latter  through 
the  open  chuck  until  it  comes  into  contact  with  the  gage  or 
stop  H2.  Just  before  lever  B2  has  reached  the  forward  end  of 
its  stroke,  and  after  the  bar  of  stock  has  come  into  contact 
with  the  stop,  the  cam  lever  U\  closes  the  chuck,  so  that  the 
bar  of  stock  is  securely  held  in  its  position  preparatory  to  being 
operated  upon  by  the  cutting  tool.  The  holder  for  stop  H2 


52  MULTIPLE-SPINDLE   DESIGNS 

can  be  adjusted  along  the  hexagonal  rod  J2  and  the  stop  is 
moved  into  or  out  of  alignment  with  the  spindle  by  a  cam  L2 
which  engages  the  dog  or  lever  K2. 

Mechanism  for  Threading.  —  When  cutting  a  right-hand 
thread,  the  work-spindle  is  stopped  in  the  third  position 
opposite  the  threading  spindle,  which  is  revolved  at  the  proper 
speed  for  the  size  and  pitch  of  the  thread  and  the  metal  being 
cut.  When  the  thread  is  finished,  the  threading  spindle  is 


Fig.  8.    Gears  arranged  to  Drive  the  Right-hand  Threading  Mechanism 
at  its  Slowest  Speed 

stopped  and  the  work-spindle  is  again  rotated,  allowing  the 
threaded  piece  to  run  the  tool  off  freely.  The  die  or  tap  is  not 
forced  onto  the  work,  but  is  advanced  by  the  pitch  of  the 
thread.  The  threading  speed  is  entirely  independent  of  the 
spindle  speed  for  the  other  cutting  operations.  When  starting 
to  cut  a  thread,  the  die  is  given  a  positive  start  by  means  of 
a  cam-controlled  lever.  Change  of  speed  for  the  die  spindle 
is  obtained  by  sliding  the  driving  gear  into  mesh  with  the 
direct  driving  gear  on  the  spindle  for  the  high  speed,  and  into 
mesh  with  a  compound  driving  gear  for  a  slower  speed.  The 
work  spindles  are  stopped  one  at  a  time  as  the  cylinder  indexes 


NATIONAL-ACME   SCREW  MACHINE 


53 


them  to  the  third  position,  by  the  action  of  a  cam  on  drum  W\, 
Fig.  2,  which  disconnects  the  friction  clutch  KI  that  nor- 
mally engages  the  spindle-driving  gear  It.  When  the  friction 
clutch  is  disengaged,  the  driving  gear  runs  freely  while  the 
spindle  is  locked  stationary  for  the  threading  operation.  The 
length  of  time  that  the  work-spindle  must  be  held  stationary 


Fig.  9.   View  of  the  Main  Tool-head,  showing  the  Right-hand  Threading  Mechanism 

in  the  third  position  is  determined  by  the  duration  of  the 
threading  or  other  special  operation  to  be  formed. 

Rotation  of  the  Threading  Spindle.  —  The  threading  spindle 
is  rotated  from  the  main  driving  shaft  HI,  through  the  ar- 
rangement of  gearing  shown  in  Fig.  8.  A  slow  and  a  fast  speed 
may  be  obtained  for  each  feed  of  the  work-spindle,  the  slow- 
speed  gearing  being  shown  in  place  in  Fig.  8.  When  a  shoe  at 
RS,  Fig.  9,  is  in  the  groove  S3  (see  Fig.  8)  of  the  sliding  gear, 


54  MULTIPLE-SPINDLE  DESIGNS 

the  drive  is  transmitted  through  gears  T3,  £/3,  and  F3  to  the 
gear  Ws  on  the  threading  spindle,  rotating  the  latter  at  its 
slowest  speed.  When  the  shoe  R$  is  engaged  with  groove  A4 
of  the  sliding  gear,  the  drive  is  direct  from  this  gear  to  gear  W^ 
thus  rotating  the  spindle  at  its  fastest  speed,  which  is  used 
for  threading  brass  or  cutting  very  fine  threads  on  soft  steel. 
When  it  is  desired  to  prevent  the  threading  spindle  from 
rotating,  the  shoe  jR3  is  drawn  up  and  gear  C3  slid  out  of  en- 
gagement with  the  other  gears.  The  threading  spindle  P2 
(Fig.  9)  is  driven  by  a  block  C4  that  engages  an  adjustable  pin 
jE4.  This  pin  may  be  adjusted  out  when  the  forward  travel 
of  the  threading  tool  must  be  faster  than  the  speed  at  which 
the  main  tool-slide  is  traveling. 

Mechanism  for  Starting  Threading  Die.  —  When  cutting 
a  thread,  the  die  or  tap  is  not  forced  onto  the  work,  but  is 
advanced  by  the  thread  after  being  given  a  positive  start  by 
a  cam-controlled  mechanism  so  that  a  poor  first  thread  will 
be  avoided.  Just  as  the  threading  operation  begins,  the  cam- 
operated  lever  Nt,  Fig.  9,  causes  the  roller  74  to  engage  the 
swinging  lever  H±,  which,  through  the  plunger  G4,  pushes  the 
threading  spindle  forward.  In  this  way,  the  threading  tool  is 
given  a  positive  start;  then  the  threading  tool  " leads"  onto 
the  work  as  far  as  the  thread  is  to  be  cut.  The  main  tool- 
slide  then  recedes,  but  the  threading  spindle  P2  is  prevented 
from  moving  backward  by  the  grip  of  the  threading  die  or 
tap,  so  that  the  coil  spring  P4  is  compressed.  As  the  tool- 
slide  moves  backward,  the  pawl  ()4  engages  ratchet  R±  on  the 
rear  end  of  the  threading  spindle,  thus  preventing  the  latter 
from  rotating,  so  that,  as  the  work-spindle  rotates,  the  thread- 
die  is  backed  off  of  the  work.  The  spring  P4,  which  was  com- 
pressed by  the  backward  movement  of  the  tool-slide,  then 
returns  the  threading  spindle  to  its  normal  position. 

Cutting  a  Left-hand  Thread.  —  When  cutting  a  left-hand 
thread  on  the  Acme  machine,  slight  alterations  are  necessary 
on  the  threading  spindle,  and  both  spindles  revolve,  the  die 
spindle  rotating  slowly  and  the  stock  spindle  at  the  regular 
speed.  As  the  work-spindle  is  rotated  faster  than  the  thread- 


DAVENPORT  FIVE-SPINDLE  MACHINE  55 

ing  spindle,  there  is  a  relative  motion  between  the  two  spindles, 
the  work-spindle  gaining  on  the  threading  tool  so  that  a  thread 
can  be  cut.  For  backing  off  a  die,  the  stock  is  stopped  and  the 
threading  spindle  continues  to  run,  which  removes  the  tool 
from  the  work. 

Use  of  Opening  Dies.  —  Long  outside  threads  or  those  that 
are  extremely  coarse  or  fine  can  be  cut  to  particular  advan- 
tage by  using  an  automatic  or  self-opening  die-head.  On 
the  Acme  machine,  the  die-head  is  revolved  while  cutting  and 
is  opened  automatically  and  closed  by  cam  movements  while 
rotating.  The  mechanism  for  timing  the  automatic  opening 
of  the  die  and  closing  it,  for  the  threading  operation,  is  attached 
to  the  main  tool-slide  on  the  cut-off  side  of  the  machine.  The 
die-head  operates  in  the  regular  threading  position. 

Davenport  Automatic  Screw  Machine.  —  The  multiple- 
spindle  automatic  screw  machine  shown  in  Fig.  10  is  built  by 
the  Davenport  Machine  Tool  Co.,  New  Bedford,  Mass.  This 
machine  has  five  work-holding  spindles  and  is  so  designed  that 
each  tool  is  controlled  independently  by  a  separate  cam,  and 
the  travel  of  each  tool  may  be  varied  without  changing  the 
cam  which  operates  it.  The  five  spindles  are  mounted  in  the 
spindle  head  A  (Fig.  n)  and  the  five  tool  spindles  are  sup- 
ported by  the  frame  B.  In  addition  to  the  five  tool  spindles 
for  holding  end-working  tools,  there  are  two  horizontal  cross- 
slides  K  and  L  (Fig.  12)  and  two  swinging  arms  M  and  N  for 
operating  forming  and  cutting-off  tools.  The  mechanism  for 
driving  the  work-spindle  and  actuating  the  tool  spindles,  and 
cross-slides  at  different  rates  of  speed,  as  well  as  other  impor- 
tant features  of  the  machine,  will  be  described. 

Method  of  Driving  Spindles.  —  The  five  work-spindles  are 
driven  from  a  belt  pulley  J  (Fig.  13)  at  the  rear  of  the  machine, 
which  transmits  motion  to  them  through  change-gears  selected 
in  accordance  with  the  speed  required.  These  change-gears 
drive  a  large  gear  C,  Fig.  n,  which  has  internal  gear  teeth 
that  mesh  with  the  smaller  gears  D  mounted  on  the  various 
spindles.  This  outer  internal  gear  has  a  bearing  on  the  hubs 
of  the  spindle  gears  at  the  pitch  diameter,  giving  a  free-running 


MULTIPLE-SPINDLE  DESIGNS 


Fig.  10.  Davenport  Five-spindle  Automatic  Screw  Machine 

rolling  bearing.     The  change-gears  provide  for  eight  spindle 
speeds  ranging  from  600  to  1500  revolutions  per  minute. 

Operation  of  Tool  Spindles.  —  The  end-working  tools  are 
mounted  in  sliding  spindles,  each  of  which  is  operated  by  a 
separate  cam.  These  cams  are  mounted  on  the  shaft  E  (Fig.  1 1), 
and  actuate  the  levers  F,  there  being  one  lever  for  each  spindle. 
The  connecting-rods  G  extending  from  each  spindle  to  its 
operating  lever  are  attached  to  adjustable  blocks  H  on  the 


DAVENPORT   FIVE- SPINDLE   MACHINE 


57 


^^-^ 


58  MULTIPLE-SPINDLE  DESIGNS 

levers,  and,  by  changing  the  position  of  these  blocks,  each 
tool  is  made  to  advance  the  same  amount  as  the  throw  of  the 
cam  which  operates  it,  or  a  less  amount,  down  to  one-half  the 
throw  of  the  cam.  The  face  of  each  lever  is  graduated  to 
indicate  the  movement  of  the  tool  relative  to  the  cam  throw. 
For  instance,  a  cam  for  turning  a  maximum  length  of  2  inches 
has  a  rise  or  throw  of  2  inches,  but  it  is  equally  effective  for 
turning  a  length  of  i  inch,  the  reduction  being  obtained  by 
simply  setting  the  block  on  the  cam  lever  to  the  0.5  division. 
When  the  block  is  set  at  graduation  i.o,  the  tool  moves  a  dis- 
tance equal  to  the  cam  throw.  The  tool  spindles  may  be  ad- 
justed lengthwise  for  varying  the  operating  position  of  each 
tool  by  a  turnbuckle  connection  between  the  cam  lever  and  the 
spindle.  The  curved  surface  on  the  lever  provides  that  the 
tool  in  its  forward  position  will  be  the  same  distance  from 
the  spindle  regardless  of  where  the  block  H  is  clamped  to  the 
lever.  There  are  seventeen  cams  furnished  with  the  machine 
and  these  cover  the  work  ordinarily  done  on  it.  For  large 
quantities  of  certain  kinds  of  work,  it  is  well  to  use  special 
cams. 

Cross-slides  and  Swinging  Arms.  —  Each  horizontal  cross- 
slide  and  swinging  arm  is  operated  by  a  separate  cam,  two  of 
which  are  mounted  on  the  front  camshaft  O  and  two  more  on 
the  rear  camshaft  P.  Motion  is  transmitted  to  the  arms  M, 
N,  and  slides  K,  L,  through  levers  and  connecting  links  which 
have  the  same  adjustment  as  the  levers  that  actuate  the  end- 
working  tools.  These  arms  and  slides  provide  for  one  cutting- 
off  tool  and  three  forming  tools,  where  they  are  required,  or 
more  than  one  tool  can  be  used  for  cutting  off,  the  arrange- 
ment depending  upon  the  nature  of  the  work.  Circular  form- 
ing and  cutting-off  tools  are  generally  used  and  are  shown  in 
position  opposite  four  of  the  spindles.  Each  toolpost  has  a 
stop-screw  for  regulating  the  size  of  the  work  formed,  the  same 
as  on  a  single-spindle  machine,  and,  in  addition,  an  adjusting 
screw  or  compensating  stop,  which  will  be  described  later. 

Driving  Mechanism  for  Camshaft.  —  The  front  and  rear 
camshafts  for  the  cross-slides  and  swinging  arms,  and  the  cam- 


DAVENPORT  FIVE-SPINDLE  MACHINE 


59 


shaft  at  the  end  of  the  machine  for  actuating  the  tool  spindles, 
are  all  driven  from  a  feed-shaft  Q  (Fig.  13)  extending  along  the 
rear  of  the  machine.  This  feed-shaft,  in  turn,  is  rotated  from 
the  main  driving  shaft  through  a  friction  clutch  R  that  is  con- 
trolled by  a  hand  lever  at  the  left-hand  side  of  the  machine 
in  front.  The  friction  clutch  is  held  into  engagement  by  a 
spring  to  allow  it  to  slip  in  case  of  accident.  The  rear  feed- 
shaft  Q  drives  the  shaft  5  (Fig.  n)  which  extends  across  the 


Machinery 


Fig.  12.   Cross-slides  and  Swinging  Arms  of  Davenport  Machine 

machine.  This  shaft  has  right  and  left-hand  worms  which 
mesh  with  worm-wheels  T  mounted  on  the  front  and.  rear 
cross-slide  camshafts.  Bevel  gears  at  the  sides  of  these 
worm-wheels  mesh  with  corresponding  bevel  gears  on  cam- 
shaft £,  and  thus  rotate  the  camshaft  which  imparts  movement 
to  the  end-working  tool  spindles.  The  speed  at  which  the 
three  camshafts  revolve  is  controlled  by  change-gears  at  U 
(Fig.  13)  which  enable  the  time  in  seconds  that  is  required 
to  make  one  piece  to  be  varied  from  3  to  20  seconds,  increas- 


6o  MULTIPLE-SPINDLE  DESIGNS 

ing  by  \  second  up  to  7  seconds,  and  then  by  i -second  incre- 
ments up  to  20  seconds,  which  is  the  maximum  time  allowed. 

Indexing  the  Spindle  Head.  —  The  head  containing  the 
five  spindles  is  indexed  by  a  rod  which  carries  two  pawls  and 
is  operated  at  the  right  moment  by  a  crank  disk  mounted  on 
the  indexing  shaft  that  extends  along  the  front  of  the  machine. 
This  indexing  shaft  derives  its  movement  from  the  handwheel 
shaft  (see  Fig.  10)  which  is  driven  continuously  when  the  feed 
driving  clutch  of  the  machine  is  engaged.  An  indexing  clutch 
is  disengaged  except  when  the  work-spindle  head  is  to  be 
indexed.  When  the  cam  for  starting  the  index  comes  into  con- 
tact with  this  clutch  at  each  revolution  of  the  shaft,  the  clutch 
is  engaged  and  the  shaft  for  indexing  the  head  is  rotated  one 
complete  revolution.  The  feed  cams  for  feeding  the  tools  are 
stationary  during  the  indexing  of  the  spindle  head. 

Spindle  Head  Locking  Mechanism.  —  The  spindle  head  is 
locked  in  position  by  a  lever  which  has  a  notched  shoe  that 
successively  engages  locking  blocks  on  the  spindle  head,  as 
these  are  indexed  in  position.  The  locking  lever  is  pulled  out 
of  engagement  and  also  pushed  back  by  a  positive  action. 
In  addition  to  the  locking  lever,  the  spindle  head  is  also 
clamped  by  a  rod  which  is  drawn  downward  by  the  action 
of  a  cam  surface  and  serves  to  tighten  the  front  bearing  cap, 
thus  holding  the  head  rigidly  while  the  tools  are  in  operation. 

Stock  Stop.  —  The  stock  is  fed  through  the  spindles  against 
a  stop  which  is  made  of  a  part  of  the  first  turning  or  other  end- 
working  tool.  The  length  that  the  cams  feed  the  stock  is 
controlled  by  a  nut  on  the  left-hand  end  of  the  shaft,  and  the 
stock  stop  is  adjusted  by  a  screw  near  the  lower  front  sliding 
spindle.  The  bars  of  stock  rotate  inside  of  a  wooden  tube, 
instead  of  in  gas  pipes,  so  as  to  avoid  excessive  noise  and 
marring  the  surface  of  the  material. 

Compensating  Stops.  —  In  order  to  insure  that  the  tools 
on  the  swinging  arms  and  cross-slides  will  be  located  accu- 
rately, with  reference  to  the  different  spindles,  the  Davenport 
multiple-spindle  machine  is  equipped  with  what  are  known  as 
compensating  stops.  These  stops  consist  of  a  series  of  pins  V 


DAVENPORT   FIVE-SPINDLE   MACHINE 


6l 


62  MULTIPLE-SPINDLE  DESIGNS 

(Fig.  12)  which  project  from  the  periphery  of  a  disk  which  is 
secured  to  the  front  end  of  the  spindle  head.  There  are  four 
separate  stops  for  each  spindle;  two  are  for  the  front  cross- 
slide  and  swinging  arm  and  there  are  two  additional  stops  for 
the  back  cross-slide  and  rear  arm,  which  are  utilized  when  the 
spindle  has  been  indexed  around  to  the  rear  position.  These 
pins  or  stops  are  engaged  by  additional  stops  upon  the  swing- 
ing arms  and  tool-slides  and  the  adjustment  of  each  stop  is 
such  that  the  cutting  edges  of  the  tools  are  accurately  located 
relative  to  the  axis  of  each  spindle  when  the  stops  are  in  en- 
gagement. In  this  way,  each  tool  is  positively  located,  and 
any  slight  inaccuracy,  due  either  to  constructional  defects  or 
wear  in  the  machine,  is  automatically  compensated  for,  after 
the  stops  have  been  adjusted. 

Method  of  Cutting  Threads.  —  When  cutting  threads  on 
the  machine  illustrated  in  Fig.  10,  the  work-spindles  are  not 
stopped  or  reversed.  The  spindle  carrying  the  die  or  tap  is 
revolved  in  the  same  direction  as  the  work-spindle,  but  at  a 
slower  speed  when  running  the  die  on,  and  at  a  faster  speed 
for  backing  it  off  of  the  finished  thread.  The  speed  of  a  die 
or  tap  when  cutting  is  about  three-fourths  of  the  spindle  speed, 
so  that  the  actual  threading  speed  is  one-fourth  of  the  spindle 
speed  in  revolutions  per  minute,  and,  as  the  diameters  that 
are  threaded  are  usually  quite  small,  the  actual  surface  speed 
for  cutting  the  threads  is  low  enough  to  insure  smooth  threads 
and  durability  for  the  dies.  When  backing  off  a  threading 
die  or  removing  a  tap  from  a  hole,  the  threading  spindle  re- 
volves rapidly. 

The  mechanism  for  driving  the  threading  spindle  is  shown 
in  Fig.  13.  The  long  "threading  shaft"  W  is  driven  from  the 
belt  pulley  shaft  at  the  rear,  through  change-gears,  as  shown. 
This  long  shaft  carries  the  male  part  of  two  friction  clutches 
which  engage  either  of  two  friction  clutch  gears  of  different 
diameters.  These  clutch  gears,  in  turn,  transmit  motion  to 
the  threading  spindle  at  the  different  speeds  required  for 
running  a  die  on  or  for  backing  it  off  of  the  work.  Thus,  when 
cutting  a  thread,  the  slow-speed  gear  is  engaged;  the  clutch 


DAVENPORT   FIVE-SPINDLE   MACHINE  63 

is  shifted  to  engage  the  high-speed  gear  when  the  thread  has 
been  cut  to  the  required  length,  by  means  of  a  cam  which 
actuates  the  clutch  through  the  lever  X.  In  the  illustration, 
the  threading  clutch  is  shown  engaged  for  running  a  die  off 
of  right-hand  threads. 

Work  for  which  Camshaft  Rotates  Continuously.  —  For 
ordinary  operations,  the  camshafts  for  feeding  the  tools  are 
stopped  when  the  spindle  head  is  indexed,  as  previously  men- 
tioned. For  some  classes  of  work,  however,  it  is  preferable 
to  arrange  the  machine  so  that  the  camshafts  rotate  continu- 
ously. For  instance,  many  pieces  can  be  made  from  brass 
rods,  in  2,  23,  or  3  seconds,  and,  for  these  rapid  jobs,  the  ma- 
chine is  equipped  with  special  cams  which  do  not  stop  revolv- 
ing when  the  head  is  indexed,  thus  saving  a  fraction  of  a 
second  on  each  piece  of  work.  In  order  to  operate  the  machine 
in  this  way,  the  roll  on  the  lever  operated  by  cam  F,  Fig.  n, 
is  removed  and  attached  to  the  outside  of  the  lever  for  safe 
keeping.  When  this  change  is  made,  the  feed  clutches  on  the 
handwheel  shaft  are  not  disconnected  during  the  indexing  of 
the  head;  the  cams  for  feeding  the  tools  then  revolve  con- 
stantly and  are  so  shaped  that  the  tools  remain  in  their  back 
positions  during  the  indexing  of  the  head.  The  tools  arrive 
at  their  working  position  before  the  crankshaft  which  indexes 
the  head  has  entirely  completed  its  revolution,  thus  effecting 
a  saving  in  time. 

Speeds  and  Feeds  Recommended.  —  The  following  feeds 
and  speeds  are  recommended  for  the  Davenport  multiple- 
spindle  automatic:  For  brass  work,  the  spindles  should  usually 
revolve  at  the  fastest  speed,  which  is  1500  revolutions  per 
minute.  When  using  high-speed  steel  tools  and  turning  soft 
iron  wire,  the  surface  speed  of  the  work  should  vary  from  about 
90  to  no  feet  per  minute;  for  soft  machine  steel,  from  80  to 
100  feet  per  minute;  for  tool  steel,  from  20  to  30  feet  per  min- 
ute. Especially  heavy  cuts  will  require  slower  speeds  than 
those  listed.  For  turning  ordinary  screw  stock,  the  surface 
speed  is  usually  100  feet  per  minute.  These  speeds  are  ordi- 
narily used  in  conjunction  with  fine  feeds  varying  from  0.004 


64 


MULTIPLE-SPINDLE  DESIGNS 


to  o.oio  inch    for  turning;    from  0.0005   to  0.0015  mcn  for 
forming  and  cutting  off. 

Hayden  Automatic  Screw  Machine.  —  The  five-spindle 
automatic  screw  machine  shown  in  Fig.  14  (built  by  the  Cin- 
cinnati Automatic  Machine  Co.)  has  incorporated  in  its  de- 
sign several  distinctive  features.  The  five  spindles,  which 


Fig.  14.   Hayden  Five-spindle  Automatic  Screw  Machine 

revolve  in  a  forward  direction,  thus  permitting  the  use  of 
right-hand  tools,  such  as  drills,  etc.,  are  driven  either  from  a 
constant-speed  motor,  or  by  a  single  belt  pulley  A,  at  the 
rear,  which  transmits  motion  to  the  spindles  through  a  geared 
speed-changing  mechanism,  at  B  (Fig.  15)  of  the  tumbler- 
gear  design.  The  end-working  tools,  such  as  box-tools,  drills, 
reamers,  etc.,  are  held  in  spindles  which  are  operated  inde- 


HAYDEN  FIVE-SPINDLE  MACHINE 


66  MULTIPLE-SPINDLE  DESIGNS 

pendently  by  cams  that  are  a  permanent  part  of  the  machine 
and  are  adjustable  for  varying  the  feed  of  each  tool  in  accord- 
ance with  its  work.  Four  cross-slides  are  provided  for  holding 
either  circular  tools,  rectangular  forming  tools,  knurling  tools, 
thread  rolls,  a  cross-drilling  attachment,  or  combinations 
tools.  The  cams  for  operating  all  the  cross-slide  and  end- work- 
ing tools  are  held  on  slides  and  are  actuated  by  a  master  cam 
which  imparts  to  each  slide  a  reciprocating  motion. 

Spindle  Chuck.  —  The  chucks  or  collets  of  the  machine 
shown  in  Fig.  14  are  of  the  draw-back  type,  but  they  are  held 
in  a  stationary  position  endwise  while  the  closing  member  is 
pushed  forward  over  the  chuck  for  tightening  it  upon  the 
stock.  When  a  chuck  of  the  "push-out"  type  is  closed,  it 
grips  the  stock  while  moving  forward,  because  the  tightening 
of  the  chuck  depends  upon  this  forward  motion.  By  designing 
the  chuck-closing  mechanism  so  that  the  outer  chuck-closing 
member  is  pushed  forward  instead  of  the  chuck,  it  is  claimed 
that  excessive  strains  on  the  mechanism,  resulting  from  the 
movement  of  the  stock  after  it  is  partially  gripped  by  the 
chuck,  are  eliminated.  The  chucks  are  opened  and  closed  and 
the  stock  fed  forward  by  cams  on  the  master  cam-drum  C  at 
the  end  of  the  machine.  Adjustment  for  feeding  the  stock  to 
different  lengths  is  made  by  a  screw  in  the  master  drum.  By 
the  shifting  of  a  lever,  the  machine  can  be  made  to  run  in  the 
usual  manner  without  feeding  any  stock  or  operating  the 
chucks,  which  is  convenient  when  setting  up  the  machine  or 
when  testing  the  size  turned  by  any  tool  after  the  cutters  have 
been  sharpened,  etc. 

Operation  of  the  Master  Cam.  —  The  master  cam-drum  C, 
which  imparts  motion  to  the  cross-slide  and  the  tool  spindles, 
has  two  speeds.  This  master  cam-drum  revolves  at  a  uni- 
formly fast  speed,  for  three-quarters  or  its  circumference, 
this  movement  requiring  one  and  one-half  second.  The  re- 
maining one-fourth  of  the  master  cam-drum  circumference  is 
utilized  in  operating  the  cutting  tools,  and  the  speed  of  rota- 
tion is  reduced  in  accordance  with  the  nature  of  the  machining 
operations,  by  means  of  a  geared  feed:box  D  at  the  front  of  the 


HAYDEN  FIVE-SPINDLE   MACHINE 


67 


machine.  While  the  master  cam  is  operating  at  the  fast 
speed,  the  first  action  that  occurs  is  the  withdrawing  of  all 
tools,  and,  when  these  are  back  out  of  the  way,  the  head  which 
carries  the  work-spindles  is  unlocked  and  indexed.  The 


Fig.  16.  Adjustable  Cams  of  Hayden  Automatic 

chuck  holding  the  stock  from  which  a  finished  piece  has  been 
severed  is  opened  and  the  stock  fed  against  a  stop,  after  which 
the  chuck  is  closed;  these  movements  occur  simultaneously 
with  the  indexing  and  are  followed  by  the  locking  of  the 


68  MULTIPLE-SPINDLE  DESIGNS 

head  and  the  bringing  of  all  tools  into  position  for  starting 
another  series  of  operations.  At  this  point,  the  speed  of  the 
master  cam  is  automatically  reduced  and  continues  to  rotate 
at  this  slower  speed  until  the  tools  have  completed  their  work 
and  are  ready  to  be  withdrawn  again;  therefore,  it  will  be  seen 
that  the  time  required  for  finishing  a  part  is  equal  to  the  time 
necessary  for  the  cutting  operations,  plus  a  constant  period 
of  one  and  one-half  second  (three  seconds  on  preceding  design) 
while  the  master  cam  is  rotating  three-fourths  of  a  revolution 
at  the  fast  speed. 

Adjustable  Cams.  —  The  cams  for  operating  the  cross- 
slides  and  the  tool  spindles  of  the  machine  shown  in  Fig.  14 
are  in  the  form  of  a  slide  or  wedge  having  a  hinge  or  swivel 
point  at  one  end.  The  arrangement  of  these  cams  for  the  end- 
working  tool  spindles  is  shown  by  the  detailed  view,  Fig.  16. 
The  five  cams  E  for  the  end-working  tool  spindles  are  carried 
by  a  slide  F  which  is  moved  in  a  direction  parallel  with  the 
tool  spindles,  by  the  master  cam  C  at  the  opposite  end  of 
the  machine.  Each  cam  E  transmits  motion  to  the  tool 
spindle  which  it  controls,  by  means  of  vertical  rods  G,  having 
rack  teeth  at  their  upper  ends  which  engage  pinions  H  that 
mesh  with  rack  teeth  on  the  tool  spindles.  The  lower  ends  of 
these  vertical  rods  G  are  equipped  with  rollers  that  bear  against 
the  cams  E  and,  as  the  latter  are  moved  by  the  master  cam, 
each  tool  spindle  is  also  moved  longitudinally  an  amount 
depending  upon  the  inclination  of  the  particular  cam  E  by 
means  of  which  it  is  operated.  The  angular  position  of  each 
cam  is  varied  in  accordance  with  the  feed  required  by  the  tool, 
by  adjusting  screws  /.  With  this  arrangement,  special  cams 
are  not  required  for  each  job,  and  the  only  cams  furnished 
with  the  machine  are  those  which  form  a  permanent  part  of  it. 

The  four  cross-slides  are  also  operated  by  separate  cams, 
the  inclination  of  which  may  be  varied  for  regulating  the 
feeding  movement  of  each  cross-slide  independently.  These 
cams  L  (Fig.  14)  also  transmit  motion  to  the  cross-slides 
through  vertical  rods  K  having  rack  teeth  at  their  upper  ends 
which  engage  pinions  meshing  with  racks  attached  to  the 


HAYDEN  FIVE-SPINDLE  MACHINE  69 

cross-slides.  The  cams  L  are  carried  by  slides  which  receive 
their  motion  from  the  master  cam-drum  C. 

Cross-slide  Stops.  —  Each  cross-slide  has  an  adjusting  screw 
and  a  separate  stop  on  the  outside  of  the  revolving  head. 
These  stops  are  adjustable  and  provide  means  to  compensate 
for  any  slight  wear  which  may  occur,  although,  after  having 
once  been  correctly  set,  they  should  not  require  adjustment 
for  a  considerable  period.  Each  slide  is  provided  with  a  swivel 
to  enable  work  to  be  formed  tapering  or  for  correcting  a  taper- 
ing cut.  Each  slide  also  has  a  screw  for  crosswise  adjustment. 

Indexing  and  Locking  Mechanism.  —  The  head  is  indexed 
by  a  crank  and  slot  mechanism,  insuring  an  easy  starting  and 
stopping  movement,  in  order  to  avoid  excessive  vibration  and 
jar.  The  locking  pin  for  the  spindle  head  is  located  at  the 
bottom  near  the  chucking  end,  and  has  one  flat  side  and  one 
angular  side  so  that  the  latter  pushes  the  head  around  until 
the  flat  side  comes  into  contact  with  the  locating  block.  The 
head  may  be  unlocked  when  it  is  desired  to  index  or  revolve  it 
by  hand. 

Time  Required  for  Making  One  Piece.  —  As  previously 
explained,  the  master  cam-drum  C,  Figs.  14  and  15,  controls 
the  movements  of  all  cutting  tools  and  completes  all  of  the 
cutting  operations  while  it  is  turning  one-fourth  of  a  revolu- 
tion; therefore,  the  time  required  to  make  one  piece  depends 
upon  the  speed  at  which  the  master  cam  rotates  during  this 
one  quarter  revolution.  This  speed  is  regulated  by  the  shift- 
ing of  two  tumbler  gears  located  in  the  case  D  in  front  of  the 
machine.  By  means  of  these  gears,  20  different  speeds  may 
be  obtained  which  give  periods  of  time  ranging  from  i\  to  36 
seconds.  A  plate  or  table  attached  to  the  machine  shows, 
opposite  each  unit  of  time  and  under  the  different  spindle 
speeds  available,  the  number  of  spindle  revolutions  during 
that  particular  period  of  time,  which,  of  course,  is  equivalent 
to  the  number  of  revolutions  available  for  each  operation. 
After  deciding  the  order  of  the  operations  and  which  opera- 
tion requires  the  greatest  number  of  spindle  revolutions  (which 
may  be  found  by  dividing  the  length  of  the  cut  by  the  feed 


MULTIPLE-SPINDLE  DESIGNS 


GRIDLEY  FOUR-SPINDLE  MACHINE  71 

per  revolution),  the  total  number  of  revolutions  per  operation 
is  obtained.  Then  referring  to  the  plate  or  table,  the  nearest 
number  of  spindle  revolutions  is  located  in  the  column  headed 
by  the  spindle  speed  which  is  suitable  for  the  work  to  be  pro- 
duced ;  opposite  this  number  will  be  found  the  time  in  seconds 
required  for  machining,  and  also  letters  indicating  the  respec- 
tive positions  of  the  tumbler-gear  levers.  There  are  sixteen 
changes  of  spindle  speeds  obtained  by  shifting  gears  in  the 
speed-box  B  at  the  rear. 

Thread  Cutting  Operations.  —  The  top  spindle  of  the 
machine  illustrated  in  Fig.  14  is  usually  used  for  thread  cut- 
ting. If  threading  operations  are  not  necessary,  however,  this 
spindle  may  be  converted  into  a  regular  tool  spindle  or  it  may 
be  used  for  high-speed  drilling.  When  cutting  a  right-hand 
thread,  the  spindle  which  holds  the  die  is  revolved  in  the  same 
direction  as  the  work-spindle,  but  at  three-fourths  of  the 
spindle  speed,  whatever  that  speed  may  be,  so  that  the  actual 
threading  speed  is  equivalent  to  one-fourth  of  the  spindle 
speed.  At  a  fixed  time,  which  is  three-fourths  of  the  total 
time  required  for  making  a  part,  the  spindle  is  caused  to  stop 
instantly,  and  as  the  die  continues  to  revolve,  it  is  unscrewed 
from  the  work.  When  cutting  a  left-hand  thread,  the  spindle 
that  is  in  line  with  the  die  is  stopped  and  the  die  revolves  at 
one-fourth  of  the  regular  spindle  speed.  After  the  thread  is 
cut,  the  spindle  is  rotated  at  full  speed,  thus  backing  the  work 
out  of  the  die.  The  mechanism  for  thread  cutting  is  self- 
contained  on  the  machine  and  the  machine  is  readily  changed 
for  cutting  left-hand  threads. 

Gridley  Multiple-spindle  Automatic  Screw  Machine.  — 
The  Gridley  multiple-spindle  automatic  screw  machines  have 
four  spindles,  the  ij-  by  5^-inch  size  being  shown  in  Fig.  17. 
These  spindles  are  driven  constantly  in  one  direction  from  a 
driving  shaft  at  the  center  of  the  spindle-carrying  cylinder. 
This  shaft  is  provided  with  a  gear  which  meshes  with  a  gear 
on  each  spindle  and  is  driven  through  change-gears  from  a 
pulley  A  running  at  a  constant  speed.  This  pulley  may  be  con- 
nected with  an  overhead  countershaft  or  be  driven  from  a  motor. 


MULTIPLE-SPINDLE  DESIGNS 


GRIDLEY  FOUR-SPINDLE   MACHINE  73 

The  four  work-spindles  are  mounted  in  a  spindle  carrier 
which  extends  from  one  end  of  the  machine  to  the  other.  This 
spindle  carrier  is  given  an  indexing  movement  each  time  the 
tools  have  completed  their  work  and  have  been  withdrawn. 
In  this  way,  each  of  the  work-spindles  is  brought  into  align- 
ment with  the  various  tools  held  on  the  tool-slide  B,  which 
is  fed  forward  and  quickly  withdrawn  by  a  cam.  After  each 
indexing  of  the  spindle  carrier,  the  tool-slide  moves  forward 
and  each  tool  or  set  of  tools  performs  the  required  operation. 
The  tool-slide  is  then  withdrawn  and  the  spindle  carrier  in- 
dexed to  locate  each  spindle  into  alignment  with  a  different 
tool  or  set  of  tools.  A  finished  piece  is  produced  every  time 
the  tool-slide  moves  forward.  A  Geneva  stop  mechanism  is 
employed  for  indexing  the  spindle-carrying  cylinder.  With 
this  mechanism,  the  starting  and  stopping  of  the  carrier  are 
gradual,  but  the  intermediate  movement  is  rapid. 

Tool-slide.  —  The  tool-slide  B  is  mounted  upon  an  exten- 
sion D  of  the  central  part  of  the  spindle-carrying  cylinder. 
This  extension  is  supported  in  a  bearing  at  one  end  of  the 
machine  while  the  larger  diameter  which  carries  the  spindles 
is  supported  at  the  other  end,  the  tool-slide  being  mounted 
between  the  two  bearings.  With  this  arrangement,  if  either 
end  of  the  cylinder  becomes  loose  in  its  bearing,  the  align- 
ment between  the  spindles  and'  tool-slide  would  not  be  affected. 
The  tools  on  the  tool-slide  are  held  in  holders  which  are  rigidly 
bolted  to  the  slide  instead  of  being  held  by  shanks. 

Feeding  Movement  for  the  Tools.  —  The  feeding  movement 
for  the  tool- slide  which  holds  the  end- working  tools  is  derived 
from  a  cam  on  the  cam-drum  C,  Fig.  18.  The  slides  carrying 
the  forming  and  cutting-off  tools  are  operated  by  cams  on  the 
drum  E.  By  means  of  a  quick  change-gear  mechanism  con- 
trolled by  lever  F,  the  feed  may  be  varied  at  will,  while  main- 
taining a  constant  spindle  speed.  With  this  arrangement,  the 
machine  may  be  set  up  without  considering  the  rate  of  feed, 
as  the  latter  may  be  varied  afterwards  until  it  is  as  coarse  as 
conditions  will  permit. 

The  Idle  Movements.  —  After  the  tools  have  finished  cut- 


74  MULTIPLE-SPINDLE  DESIGNS 

ting,  the  withdrawal  of  the  tool-slide,  the  indexing  of  the 
spindle-carrying  cylinder,  and  the  movement  of  the  tools  for- 
ward again  to  the  position  for  cutting  are  commonly  known 
as  the  idle  or  non-productive  movements.  On  the  Gridley 
multiple-spindle  machine,  the  time  necessary  for  these  idle 
movements  is  independent  of  the  feed  used  when  the  tools 
are  cutting. 

Camshaft  and  Cams.  —  The  main  camshaft  is  parallel  to 
the  driving  shaft  and  is  driven  from  it  by  a  worm  on  the 
spindle  driving  shaft,  through  a  change-gear  box,  a  worm- 


Fig.  19.   Independent  Stops  for  Each  Spindle  Position 

shaft,  and  a  worm-gear  mounted  on  the  camshaft.  This 
shaft  carries  the  cams  for  feeding  the  tool-slide,  for  operat- 
ing the  chuck-  and  stock-feeding  mechanism,  and  also  operates 
the  mechanism  for  revolving  the  spindle  carrier  and  drives 
the  shaft  upon  which  the  forming  and  cutting-ofT  cam-drum 
E  (Fig.  1 8)  is  mounted.  The  long  cam-drum  H  operates  the 
mechanism  for  feeding  the  stock.  The  indexing  arm  /,  for 
revolving  the  spindle  carrier,  carries  a  cam  which  withdraws 
the  locking  bolt  and  indexes  the  spindle  carrier  one-fourth  of 
a  revolution  for  each  revolution  of  the  camshaft.  The  cam- 
drum  E  which  carries  the  cams  for  operating  the  cut-off  and 


NEW  BRITAIN   SIX-SPINDLE   MACHINE 


75 


7  6  MULTIPLE- SPINDLE   DESIGNS 

forming  tool-slides  has  its  axis  at  right  angles  to  the  main  cam- 
shaft and  is  driven  through  a  pair  of  bevel  gears.  The  large 
cam-drum  C  for  feeding  the  tool-slide  is  provided  with  cams 
of  three  different  leads,  and  cam  lever  K  is  set  in  one  of  three 
positions,  depending  upon  the  particular  cam  that  is  being  used. 

Stops  for  Forming  Tools.  —  Independent  stops  for  the  form- 
ing tool  are  provided  for  each  spindle  position,  so  that  the  tool 
is  moved  up  to  the  same  position  relative  to  the  spindle  each 
time  a  part  is  produced.  The  arrangement  of  these  stops  is 
shown  by  the  detailed  view,  Fig.  19.  The  stop  A,  which  is 
attached  to  the  spindle  carrier,  is  engaged  by  a  stop  B,  passing 
through  an  arm  that  is  fixed  to  the  forming  tool-slide. 

Method  of  Cutting  Threads.  —  When  cutting  threads  on 
the  Gridley  multiple-spindle  automatic,  the  die  is  held  in  a 
holder  L  (Fig.  18)  which  is  carried  by  a  slide.  This  slide  is 
fed  forward  by  a  cam  M  which  imparts  motion  to  the  slide 
through  the  bellcrank  N  and  the  connecting  link  shown,  and 
the  slide  is  returned  by  another  cam  on  drum  //.  The  die  is 
rotated  in  the  same  direction  as  the  spindle,  but  at  a  speed 
slightly  less  than  the  spindle  speed  while  the  thread  is  being 
cut;  the  die  is  then  revolved  at  a  higher  rajte  of  speed,  in  order 
to  run  it  off  of  the  work.  These  two  speeds  are  obtained  by 
means  of  two  gears  on  the  spindle  driving  shaft  which  mesh 
with  two  loose  gears  0  and  P  on  the  threading  shaft.  For 
cutting  a  thread,  the  slow-speed  gear  is  engaged  by  a  clutch 
located  between  the  two  gears,  and,  as  soon  as  the  thread  is 
completed,  this  clutch  is  shifted  to  the  high-speed  gear,  thus 
backing  off  the  die.  The  adjusting  nut  Q  controls  the  point 
at  which  the  die  is  reversed,  and  the  cam  for  re-engaging 
the  clutch  is  attached  to  a  worm-wheel  on  the  camshaft. 
Either  right-hand  or  left-hand  threads  can  be  cut  by  trans- 
posing one  connecting  link  and  changing  one  cam. 

These  machines,  at  the  present  time,  are  built  in  four  sizes: 
namely,  }  by  4^  inches;  ij  by  5^  inches;  if  by  7  inches;  and 
2\  by  7  inches. 

New  Britain  Automatic  Screw  Machine.  —  The  New 
Britain  automatic  screw  machine  shown  in  Fig.  20  has  six 


NEW  BRITAIN   SIX-SPINDLE   MACHINE 


77 


78  MULTIPLE-SPINDLE  DESIGNS 

spindles,  so  that  nine  operations  can  be  performed  simultane- 
ously on  six  pieces,  by  utilizing  both  the  end-working  and 
cross-slide  tools.  Fig.  22  shows  the  arrangement  of  the  drive. 
The  driving  shaft  is  shown  at  the  extreme  right,  and  this 
shaft  runs  at  constant  speed.  At  the  left-hand  end  of  the 
driving  shaft  there  is  a  gear  A  that  transmits  motion  to 
the  main  shaft  B  through  gear  C.  The  main  shaft  passes 
through  the  tool-slide  and  spindle  carrier,  and  at  its  extreme 
left-hand  end  ca-rries  a  gear  D  the  function  of  which  is  to  ro- 
tate the  six  spindles  through  gears  E.  The  drive  is  carried  from 
the  main  shaft  to  the  camshaft  through  a  small  pinion  F  on  the 
main  shaft,  that  meshes  with  gear  G  on  the  feed-shaft.  This 
feed-shaft  carries  a  pinion  H  that  meshes  with  an  internal 
gear  on  the  feed  cam  7.  Camshaft  /  is  rotated  through  gears 
from  the  end  of  the  feed-shaft,  and  these  gears  may  be  changed 
to  secure  any  required  speed  for  the  camshaft.  The  drive  to 
the  indexing  shaft  is  taken  direct  from  the  drive  shaft  to  the 
index  drive  shaft  K  through  spur  gearing.  The  index  shaft 
is  in  two  sections;  the  forward  section  marked  L  and  the  rear 
section  M.  (See  also  Fig.  21.)  The  forward  half  rotates  con- 
tinuously, but,  at  the  time  of  indexing,  a  clutch  connects  it 
with  the  rear  section  M  and  the  indexing  is  done  through 
spur  gearing  and  a  Geneva  motion  that  will  be  described  later. 
Power  is  carried  to  the  threading  shaft  N  (see  Figs.  21  and  22) 
through  spur  gearing  direct  from  the  main  shaft.  At  the  left- 
hand  end  of  the  threading  shaft  is  a  spur  gear  that  is  thrown 
into  mesh  with  the  driving  gear  on  the  threading  spindle,  for 
performing  the  threading  operation. 

Spindle  Construction.  —  All  of  the  spindle  thrust  is  taken 
upon  the  ball  thrust  bearings  Q  (Fig.  23)  that  are  set  into  the 
frame  of  the  spindle  carrier,  and  receive  the  thrust  of  the  ro- 
tating spindles.  The  collet  chucks,  one  of  which  is  shown  at 
R,  are  closed  on  the  " push-in"  principle,  being  forced  into 
sleeves  on  the  noses  of  the  spindles.  The  usual  mechanism 
for  closing  the  chucks  is  used,  there  being  fingers  S  that  are 
oscillated  and  throw  the  chucks  forward  into  the  sleeves. 
These  fingers  are  operated  by  clutches.  The  stock  tubes  T 


NEW  BRITAIN  SIX-SPINDLE  MACHINE  79 

are  also  of  the  usual  type,  the  work  being  seized  by  the  spring 
jaws  on  the  chuck-end  of  the  stock  tubes.  The  stock  tubes 
are  advanced  by  a  cam  mechanism  acting  through  the  sleeve 
that  may  be  seen  on  the  extreme  left-hand  end  of  the  stock 
tube.  The  main  shaft  of  the  machine  is  indicated  at  B,  and 
transmits  power  to  the  spindles  through  gear  D  that  meshes 
with  gears  E  on  the  spindles.  The  spur  gears  W  are  for  driv- 
ing the  spindles  when  in  operation  for  threading,  the  gear  W 
being  slidably  keyed  to  the  spindles.  At  all  times,  except 
when  the  spindles  are  in  the  threading  position,  these  gears 
W  are  kept  thrust  into  a  taper  seat  in  the  gears  E,  and  the 
spindles  are  driven  by  the  gear  D.  This  friction  is  maintained 
by  fingers  X  that  are  operated  by  clutches  and  yokes.  At  the 
time  of  threading,  the  clutches  are  cam-operated  so  as  to  re- 
lease fingers  X,  and  the  friction  drive  between  gears  W  and  E 
is  broken;  thus  at  this  time  the  spindles  are  not  driven  by 
the  driving  gear  D,  because  the  connection  between  gears  E 
and  W  is  broken.  For  threading,  therefore,  it  is  evident  that 
gears  W,  operated  by  a  special  driving  mechanism  to  be  de- 
scribed later,  are  responsible  for  the  rotation  of  the  spindles. 
While  the  main  shaft  B  passes  through  bronze  bushings  in 
the  spindle  carrier,  none  of  the  weight  of  the  spindle  carrier 
comes  upon  it,  this  weight  being  all  taken  on  the  spindle- 
carrier  bearings  at  V.  Six  or  more  speeds  are  available  for  the 
spindles,  and  these  are  effected  by  change-gears  that  may  be 
placed  upon  the  right-hand  ends  of  the  feed-shaft  and  cam- 
shaft, as  illustrated  in  Fig.  22. 

The  Tool-slide.  —  There  are  six  tool-holding  positions  on 
the  tool-slide  P  (Fig.  20)  which  is  operated  from  cam-drum  7. 
Upon  this  drum  are  placed  the  cams  that  govern  the  opera- 
tion of  the  slide.  These  cams  act  through  a  stud  on  the  lower 
part  of  the  tool-slide.  The  cam-drum  is  kept  free  from  back- 
lash by  a  hardened  steel  roll  supported  from  the  frame,  that 
runs  against  the  right-hand  edge  of  the  drum.  As  previously 
mentioned,  the  cam-drum  is  driven  by  an  internal  gear  and 
pinion,  shown  at  H  in  Fig.  22.  A  stud  0  (Fig.  20),  carries  a 
bevel  pinion  that  meshes  with  a  corresponding  bevel  gear  on 


8o 


MULTIPLE-SPINDLE  DESIGNS 


the  feed-shaft  which  carries  the  small  pinion  H,  so  that  the 
cam-drum  may  be  turned  by  hand  when  setting-up  the  ma- 
chine. A  hand  lever  on  stud  Q  operates  a  clutch  for  disengaging 
the  camshaft  at  any  desired  time,  thus  stopping  the  action  of 
the  tools.  This  clutch  may  also  be  thrown  out  from  the  rear 
of  the  machine.  A  laminated  cam  is  made  use  of  on  the  feed 
drum.  This  is  a  patented  cam  construction,  in  which  the 


.THREADING   CHANGE-GEARS 


Machinery 


Fig.  22.  Diagram  showing  Arrangement  of  Driving  Mechanism  on  New 
Britain  Six-spindle  Automatic 

cam  strip  is  composed  of  three  leaves,  which  permits  of  the 
adjusting  of  one  cam  to  any  length  of  work  within  the  capacity 
of  the  machine. 

Indexing  Mechanism. -- The  indexing  of  the  machine 
shown  in  Fig.  20  is  done  at  constant  speed,  irrespective  of  the 
speed  of  the  main  shaft  or  camshaft  and  without  regard  to 
the  length  of  the  job  on  the  machine.  As  has  been  explained, 
the  index  shaft  is  in  two  sections;  the  forward  section  L 
(Figs.  21  and  22)  revolves  continuously,  and  the  rear  section  M 
revolves  only  at  the  time  of  indexing.  A  clutch  connects 
the  two  sections  of  the  indexing  shaft;  and,  at  each  revo- 


NEW  BRITAIN   SIX-SPINDLE  MACHINE 


8l 


lution  of  the  cam-drum,  this  clutch  is  tripped  by  the  small 
edge-cam  R,  Fig.  22.  When  the  clutch  is  tripped,  and  the 
rear  index  shaft  is  caused  to  turn,  gear  S  turns  gear  T  through 
exactly  one-half  revolution,  because  gear-  S  is  just  one-half 
the  diameter  of  gear  T. 

Diametrically  opposite  each  other  on  the  side  of  gear  T 
are  two  studs  that  operate  the  Geneva  gear  U  which  may  be 
more  clearly  shown  in  the  front  view,  Fig.  20.  This  gear  is 
supported,  but  not  driven,  by  the  camshaft.  The  operation 
of  the  stud  in  the  slot  in  the  Geneva  gear  turns  it  exactly  one- 
sixth  of  a  revolution,  and  as  this  gear  U  is  in  mesh  with  the 


W      E      O     EjgWV.  \   r-~—. 


Machinery 


Fig.  23.   Cross-sectional  View  of  One  of  the  Six  Spindles  of  New  Britain 
Automatic  Screw  Machine 

gear  on  the  spindle  carrier,  which  is  of  the  same  diameter,  the 
spindle  carrier  is  also  turned  one-sixth  of  a  revolution.  Just 
previous  to  the  indexing,  a  cam  and  cam  lever  operated  from 
the  camshaft  withdraw  the  locking  bolt  shown  at  V  in  Fig. 
21.  This  is  a  wide  heavy  key  that  is  normally  kept  in  contact 
with  the  spindle  carrier  by  spring  pressure,  engaging  in  one  of 
the  six  slots  equally  spaced  about  the  circumference  of  the 
spindle  carrier.  The  cam  releases  the  key,  so  that,  when  the 
spindle  carrier  has  turned  far  enough  to  engage  the  locking 
bolt,  it  jumps  into  place  and  holds  the  spindle  carrier  until 
the  time  of  next  indexing.  The  Geneva  motion  is  particularly 
adaptable  to  indexing  mechanisms  in  that  the  starting  motion 
is  slow,  gradually  accelerating  and  then  diminishing  at  the 
end  of  the  motion. 

The    Cross-slide.  —  The    cross    or    forming    slides    of    the 
machine  shown  in  Fig.  20  are  three  in  number,  operating  on 


82  MULTIPLE-SPINDLE  DESIGNS 

the  second,  third,  and  sixth  spindles.  Provision  has  also  been 
made  for  adding  a  cross-slide  to  the  fifth  spindle  if  the  work 
to  be  performed  requires  it.  Fig.  20  clearly  illustrates  the 
second  and  third  spindle  cross-slides  which  are  operated  by 
means  of  cam  levers  engaging  plate  cams  on  the  camshaft  /. 
The  rear  cross-slide  may  be  readily  seen  in  Fig.  21  and  is  used 
principally  for  cutting  off.  The  stock-feeding  and  chuck- 
closing  operations  are  performed  from  the  cam-drum  at  the 
extreme  end  of  the  camshaft.  This  operates  on  the  clutches 
that  feed  the  stock  and  close  the  chuck  on  the  spindle  in  the 
first  or  lowljj  position,  which  is  just  above  the  top  surface 
of  the  cam. 

The  Threading  Spindle.  —  The  threading  shaft  N  is 
mounted  at  the  left-hand  end  (as  viewed  in  Fig.  21)  in  a  float- 
ing bearing  that  permits  the  entire  shaft  to  be  oscillated, 
thus  allowing  the  gear  under  the  guard  at  Z  on  the  opposite 
end  to  be  thrown  into  or  out  of  mesh  with  the  spindle  gear  W, 
when  actuated  by  lever  Y  that  is  guided  by  a  cam  on  the  cam- 
shaft. The  operation  of  this  threading  shaft  is  as  follows: 
Just  before  the  spindle  carrier  is  indexed,  the  threading  shaft 
and  its  gear  are  thrown  away  from  the  spindle  to  give  the 
spindle  carrier  a  clear  path  for  indexing.  As  soon  as  the  lock- 
ing bolt  has  shot  into  place,  a  rise  on  the  cam  that  governs 
lever  Y  carries  this  lever  back  into  its  inner  position  with  the 
gear  in  mesh  with  the  gear  W  on  the  spindle  at  the  threading 
position.  Simultaneously  with  this  action,  lever  X  is  operated 
by  the  cam  on  the  camshaft  and  operates  the  spindle  clutch 
that  releases  the  spindle  driving  gear  E  (see  Fig.  23)  from  con- 
tact with  the  gear  W  that  is  now  in  mesh  with  the  gear  Z  on 
the  threading  spindle.  By  this  means  the  spindle  is  operated 
at  the  correct  threading  speed.  Before  the  indexing  takes 
place,  the  threading  shaft  is  again  swung  away  and  gear  Z  is 
thrown  out  of  mesh  with  the  spindle  gear. 

A  brake  lever  located  at  the  right  of  lever  X  (Fig.  21)  is 
operated  from  the  camshaft.  The  upper  end  of  this  lever  is 
fitted  with  a  fiber  plug  and  its  function  is  to  bear  against  the 
spindle  and  retard  rotation  just  before  the  threading-shaft 


NEW  BRITAIN  SIX-SPINDLE  MACHINE  83 

gear  Z  goes  into  mesh  with  the  spindle  gear.  On  the  left- 
hand  end  of  the  threading  spindle  is  a  reversing  shaft  by  means 
of  which  a  left-hand  rotation  may  be  given  the  shaft  when  left- 
hand  threads  are  to  be  cut.  The  threading  die  or  tap-holder 
on  the  tool-slide  is  fitted  with  a  pusher  that  presses  against 
the  rear  of  the  holder  to  engage  the  threading  die  or  tap  on 
the  work,  after  which  it  "leads"  itself  on.  Spring  fingers 
prevent  the  threading-die  holder  from  turning  when  in  action. 
This  machine  at  the  present  time  is  built  in  four  sizes;  namely, 
f  by  3!  inches;  i  by  5  inches;  if  by  7  inches;  and  2§  by  9^ 
inches. 


CHAPTER   IV 
AUTOMATIC    SCREW    MACHINE    TOOL    EQUIPMENT 

THE  various  cutting  tools  used  on  automatic  screw  machines 
for  external  and  internal  machining  operations  include  form 
tools  for  accurately  producing  irregular  shapes  in  duplicate, 
box-tools,  hollow  mills,  shaving  tools  for  light  finishing  cuts, 
recessing  tools,  drills,  reamers,  counterbores,  centering  tools, 
knurling  tools,  cutting-off  tools,  threading  dies,  taps,  etc. 
There  are  also  many  special  designs,  some  of  which  are  neces- 
sary for  making  a  given  part  on  the  screw  machine,  whereas 
others  are  used  to  obtain  a  higher  rate  of  production  than 
would  be  possible  with  regular  or  standard  tool  equipment. 
The  most  important  tools,  especially  of  the  class  that  is  adapted 
to  general  work,  will  be  described.  Most  of  these  tools  were 
designed  for  use  on  certain  screw  machines,  although  the  same 
general  types,  in  practically  all  cases,  may  be  applied  to  screw 
machines  made  by  other  manufacturers,  with  such  modifica- 
tions regarding  size,  etc.,  as  may  be  necessary  owing  to  varia- 
tions in  the  design  of  the  machine. 

Circular  Forming  and  Cutting-off  Tools.  —  When  a  part 
is  to  be  produced  on  the  automatic  screw  machine,  the  suc- 
cessive order  of  the  operations  and  the  kind  and  number  of 
the  cutting  tools  required  should  be  decided  upon  before  de- 
signing the  cams,  assuming  that  the  machine  is  of  the  type 
requiring  special  cams  for  each  job.  The  method  of  applying 
a  forming  tool  varies  somewhat  according  to  the  shape  and 
proportions  of  the  work. 

A  simple  application  of  a  circular  forming  tool  is  illustrated 
by  the  diagram  to  the  left  in  Fig.  i.  This  tool  A  is  attached 
to  a  holder  which  is  mounted  upon  the  cross-slide  of  the  ma- 
chine; the  cutting-off  tool  is  located  on  the  opposite  side,  as 
the  illustration  indicates.  The  stock  is  first  fed  out  against 

84 


FORMING  TOOLS 


the  stop  in  the  turret  and  then  the  forming  tool  A  moves  in, 
turning  the  body  and  the  conical  head;  just  as  the  tool  A  is 
finishing,  the  cut-off  tool  B  moves  in  and  severs  the  part  from 
the  bar.  The  body  of  this  screw  could  be  turned  by  a  tool 
held  in  the  turret,  but,  when  using  a  machine  of  the  Brown  & 
Sharpe  type,  a  tool  held  on  the  cross-slide  is  usually  preferable, 
because  the  work  can  be  done  more  rapidly.  This  method  is 
recommended  when  the  length  of  the  work  does  not  exceed 
i\  times  the  smallest  diameter  A  of  the  part  when  finished; 
parts  that  are  longer  than  this  are  too  flexible  to  be  turned  by 
a  cross-slide  tool. 

Another  example  is  shown  to  the  right  in  Fig.  i.     In  this 


Fig.  1.   Application  of  Forming  and  Cutting-off  Tools 

case,  the  forming  tool  C  turns  the  part  c  and  e.  Then  a  die  in 
the  turret  threads  the  end  after  which  the  tool  D  moves  in 
and  serves  the  finished  piece  from  the  bar  of  stock  and,  at  the 
same  time,  forms  the  part  d  for  the  next  screw.  The  stock  is 
then  fed  out  against  the  stop  in  the  turret  and  the  operation 
repeated. 

Methods  of  Applying  Circular  Forming  Tools.  —  When 
turning  short  screws  on  a  Brown  &  Sharpe  machine  with 
circular  forming  and  cutting-off  tools,  as  indicated  at  A 
Fig.  2,  if  the  time  utilized  by  the  tools  will  not  permit  revolv- 
ing the  turret  for  locating  the  stock  in  position  for  the  next 
successive  feeding  movement  of  the  stock,  two  sets  of  tools, 
that  is,  two  stops  and  two  die-holders  should  be  used  in  the 


86 


TOOL  EQUIPMENT 


O 


_L 


FORMING  TOOLS  87 

turret.  The  method  shown  at  B  is  not  to  be  recommended, 
because  the  feeding  of  the  stock  varies  to  such  an  extent  that 
the  forming  tool  will  break  off  the  screw  when  the  latter  has 
been  reduced  to  a  diameter  a  by  the  forming  tool,  in  case 
there  is  an  excessive  amount  to  face  off  of  the  end  of  the  stock. 
As  the  turret  would  require  to  be  indexed,  in  any  case,  to 
clear  the  arm  of  the  slotting  attachment,  the  screw  end  could 
be  finished  by  a  tool  in  the  turret  with  little  loss  of  time  as 
compared  with  the  method  shown  at  B,  although  the  latter 
may  be  employed  when  part  a  is  large  in  diameter  and  the 
screw  is  short  and  stiff. 

When  a  box-tool  or  hollow  mill  follows  the  forming  opera- 
tion, when  turning  a  comparatively  long  screw  or  bolt  as  indi- 
cated at  C,  the  forming  tool  should  be  beveled  as  at  e%  as  this 
leaves  a  beveled  shoulder  on  the  work,  so  that,  when  the  box- 
tool  or  hollow  mill  reaches  the  formed  surface,  it  completely 
removes  the  superfluous  material  as  at  C\  without  leaving 
the  objectionable  ring  which  would  be  produced  if  the  face 
of  the  forming  tool  were  square,  as  indicated  by  the  diagrams 
C2  and  C3.  This  ring  of  metal  c  prevents  the  finishing  box- 
tool  or  die  from  being  fed  up  to  the  shoulder.  The  cutting-off 
tool  should  bevel  the  end  of  the  stock  as  at  d  (diagram  C), 
so  that  the  box-tool  will  have  a  light  cut  until  the  back-rests 
have  a  good  support.  This  beveled  or  pointed  end  also  locates 
a  hollow  mill  and  equalizes  the  cutting  action  on  the  teeth. 

The  method  illustrated  at  D  may  sometimes  be  used  to 
advantage  when  making  shouldered  screws  or  other  pieces 
of  similar  form.  This  method,  however,  is  not  recommended 
when  considerable  accuracy  is  required,  because  a  slight 
eccentricity  in  the  spring  collet  would  cause  part  /  to  be  out 
of  true  with  part  g.  For  accurate  work,  the  part  g  should  be 
rough-turned  with  a  cut-off  tool  and  a  light  finishing  cut  taken 
with  a  box-tool  held  in  the  turret.  The  forming  tool  shown 
at  DI  is  so  shaped  that  it  moves  the  burr  from  the  screw-head. 

When  applying  circular  forming  tools,  the  gaging  of  the 
work  should  be  carefully  considered,  because  in  some  cases, 
when  irregular  shapes  are  to  be  formed,  it  may  be  possible  to 


88 


TOOL  EQUIPMENT 


use  a  forming  tool  which  will  greatly  simplify  the  method 
of  gaging  the  finished  work.  The  piece  shown  at  E  in  Fig.  2 
will  require  a  box-tool,  a  forming  tool,  and  a  cutting-off  tool, 
but,  when  using  the  forming  tool  shown,  it  is  simply  neces- 
sary to  measure  the  diameter  and  over-all  length,  and  the 
latter  does  not  require  to  be  very  accurate.  Another  method 
of  producing  the  same  part  is  shown  at  F;  three  tools  are  used 
as  before,  but  the  cutting-off  tool  finishes  the  work  to  length 
h,  whereas  the  box-tool  finishes  the  shoulder  to  length  k.  In 
this  case,  a  more  expensive  gage  will  be  necessary,  and  con- 
siderable extra  time  will  be  required  for  setting  up  the  tools 
after  grinding.  It  is  generally  necessary  to  provide  means 


REAR  SLIDE 

Machinery, N.Y. 


Fig.  3.   Circular  Forming  Tools  and  Holders 

for  removing  the  objectionable  burr  made  by  turning  tools, 
as  indicated  at  G.  In  order  to  remove  these  burrs,  forming 
tools  are  frequently  given  beveled  edges  as  indicated  at  Gi. 

Holder  for  Circular  Forming  and  Cutting-off  Tools.  — In 
order  to  prevent  chattering,  it  is  necessary  to  hold  a  forming 
tool  rigidly.  The  Brown  &  Sharpe  type  of  holder  shown  in 
Fig.  3  provides  a  rigid  support  for  the  tool  and  includes  suit- 
able adjustment,  provision  for  periphery  clearance,  as  well 
as  means  for  adjusting  the  tool  at  right  angles  to  the  work. 
The  tool  is  firmly  clamped  against  the  face  of  the  holder  by 
means  of  a  cap-screw  b  in  the  center  and  a  clamping  bolt  which 
grips  the  rear  side  of  the  tool  and  prevents  it  from  turning 
while  cutting. 


FORMING  TOOLS 


89 


Arrangement  of  Circular  Tools.  —  When  applying  circular 
tools  to  automatic  screw  machines,  their  arrangement  has 
an  important  bearing  on  the  results  obtained.  The  various 
ways  of  arranging  the  circular  tools,  with  relation  to  the  rota- 
tion of  the  spindle,  are  shown  at  A,  B,  C,  and  D,  in  Fig.  4. 
These  diagrams  represent  the  view  obtained  when  looking 
towards  the  chuck.  The  arrangement  at  A  gives  good  results 
for  long  forming  on  brass,  steel,  or  gun-screw  iron,  for  the 
reason  that  tjie  pressure  of  the  cut  on  the  front  tool  is  down- 
ward; the  support  is  more  rigid  than  when  the  forming  tool 
is  turned  upside  down  on  the  front  slide,  as  shown  at  B;  here 


Machinery, N.Y. 


Fig.  4.   Different  Arrangements  of  Circular  Tools 

the  stock,  turning  up  towards  the  tool,  has  a  tendency  to  lift 
the  cross-slide,  causing  chattering;  therefore,  the  arrangement 
shown  at  A  is  recommended  when  a  high  finish  is  desired. 

The  arrangement  at  B  works  satisfactorily  for  short  steel 
pieces  which  do  not  require  a  high  finish;  it  allows  the  chips 
to  drop  clear  of  the  work,  and  is  especially  advantageous 
when  making  screws,  when  the  forming  and  cut-off  tools  oper- 
ate after  the  die,  as  no  time  is  lost  in  reversing  the  spindle. 
The  arrangement  at  C  is  recommended  for  heavy  cutting  on 
large' work,  when  both  tools  are  used  for  forming  the  piece; 
a  rigid  support  is  then  necessary  for  both  tools  and  a  good 
supply  of  oil  is  also  required.  The  arrangement  at  D  is  objec- 


90  TOOL  EQUIPMENT 

tionable  and  should  be  avoided;  it  is  used  only  when  a  left- 
hand  thread  is  cut  on  the  piece  and  when  the  cut-off  tool  is 
used  on  the  front  slide,  leaving  the  heavy  cutting  to  be  per- 
formed from  the  rear  slide.  In  all  "cross-forming"  work, 
it  is  essential  that  the  spindle  be  kept  in  good  condition,  and 
that  the  collet  or  chuck  have  a  parallel  contact  upon  the  bar 
which  is  being  formed. 

Clearance  for  Circular  Tools.  —  In  order  to  provide  periph- 
ery clearance  on  circular  tools,  the  center  of  the  tool  is  lo- 
cated a  certain  amount  above  or  below  the  center  of  the 
work,  as  shown  in  Fig.  4.  On  account  of  this  offset  of  the  cut- 
ting edge,  the  actual  difference  in  the  diameters  of  different 
surfaces  of  the  forming  tool  does  not  exactly  correspond 
with  the  same  relative  dimensions  on  the  work.  For  instance, 
if  a  circular  forming  tool  has  two  or  more  diameters,  the  dif- 
ference in  the  radii  of  the  steps  on  the  tool  will  not  be  exactly 
the  same  as  the  difference  in  the  steps  on  the  work. 

There  is  a  difference  of  opinion  regarding  the  question  of 
side  clearance  for  circular  tools,  some  advocating  considerable 
clearance,  others  only  a  slight  amount,  or  no  clearance  at  all. 
When  tools  heat  up  and  "welding"  occurs,  this  may  not  be 
due  to  the  lack  of  clearance,  but  rather  to  the  poor  quality 
of  cooling  lubricant  used.  Side  clearance  is  necessary  in  some 
cases,  but  tools  made  without  clearance  should  be  ground 
smooth  on  the  sides  and  a  good  grade  of  lard  oil  used  as  a 
cutting  lubricant. 

Tool-holders  for  Flat  Forming  Tools.  —  Flat  or  straight 
forming  tools  are  used  on  automatic  screw  machines  instead 
of  circular  forming  tools,  in  some  cases,  especially  when  the 
part  to  be  formed  is  quite  large  and  a  very  rigid  tool  is  de- 
sirable. The  toolpost  shown  at  A  in  Fig.  5  is  extensively 
used  on  the  Cleveland  automatic  machine.  The  base  a  is 
bolted  directly  to  the  cross-slide  and  the  top  face  of  this  base 
is  beveled  to  an  angle  of  about  15  degrees.  The  bevel  wedge 
b  has  a  tongue  which  fits  into  a  corresponding  groove  in  the 
base  and  the  top  face  of  the  wedge  has  a  tongue  that  fits  into 
another  groove  in  the  flat  forming  tool  c.  The  forming  tool 


FORMING  TOOLS 


is  adjusted  vertically  by  screw  d,  the  head  of  which  engages 
one  of  a  series  of  slots  in  the  wedge.  The  toolpost  shown  at  B 
is  used  for  holding  light  forming  tools  or  for  cutting-off  tools 
that  are  not  of  the  blade  type.  It  consists  principally  of  a 


Fig.  5.   Two  Types  of  Flat  Forming  Tool-holders 


Fig.  6.   Open-side  Forming  Tool-holder  and  Standard  Universal  Cut-off  Tool- 
holder  for  Cut-off  Tools  of  the  Blade  Type 

clamping  strap  e,  a  base  /,  and  a  tapered  wedge  g,  which  is 
adjusted  by  screw  h. 

The  design  of  tool-holder  shown  at  A  in  Fig.  6  is  known  as 
an  open-side  forming  toolpost.  It  is  used  for  holding  forming 
tools  having  square  shanks.  The  forming  tool  is  clamped  by 
set-screw  b  and  is  adjusted  to  the  required  height  by  wedge  e 
and  screw  /.  This  type  of  toolpost  is  adapted  to  holding  inex- 
pensive forming  tools.  The  toolpost  shown  at  B  in  Fig.  6 
is  known  as  a  universal  cutting-ojj  tool-holder.  The  swinging 


Q2  TOOL  EQUIPMENT 

tool-holder  h  is  pivoted  on  bolt  it  which  also  clamps  the  holder, 
ratchet,  and  post  together.  A  threaded  stud  j  supports  the 
ratchet  k  and  this  ratchet  gives  adjustment  to  the  tool-holder 
h.  The  blade  type  of  cutting-off  tool  I  is  clamped  in  place  by 
two  bolts  m.  This  tool-holder  may  be  used  on  either  the 
front  or  the  rear  of  the  cross-slide.  As  shown  in  the  illustra- 
tion, it  is  set  for  the  rear  position.  When  it  is  to  be  used  on 
the  front  of  the  cross-slide,  the  position  of  the  tool-holder  h 
may  be  reversed  so  that  the  blade  is  located  below  the  center. 

Tools  for  Cutting  Off  Finished  Parts.  —  There  are  two 
general  types  of  tools  used  on  automatic  screw  machines  for 
cutting  off  finished  parts  from  a  bar  of  stock;  namely,  the 
blade  type  and  the  circular  type.  The  blade  type  consists 
of  a  narrow  straight  blade  which  is  clamped  in  a  suitable 
holder.  Tools  of  this  kind  serve  only  to  sever  finished  parts, 
whereas  the  circular  type  are,  in  many  cases,  so  formed  that, 
as  the  blade  cuts  off  the  finished  piece,  another  cutting  edge 
on  the  tool  either  bevels  or  rounds  the  end  of  the  part  being 
severed  or  performs  some  other  operation,  such  as  "  point- 
ing" the  bar  of  stock  or  reducing  its  diameter  at  the  end,  pre- 
paratory to  making  the  next  piece.  The  view  to  the  right  in 
Fig.  i  illustrates  how  a  cutting-off  tool  is  used  to  turn  down 
the  end  of  the  next  succeeding  piece  while  cutting  off  the  one 
that  has  just  been  finished.  Other  similar  applications  of 
circular  cutting-off  tools  are  shown  in  Fig.  2. 

The  edge  of  a  cutting-off  tool  is  ground  at  an  angle,  so  that 
it  will  sever  the  finished  part  completely  by  a  cutting  action. 
If  the  cutting  edge  were  parallel  with  the  axis  of  the  work,  the 
latter  would  break  off,  due  to  the  pressure  of  the  cut  before 
the  cutting  edge  reached  the  center,  so  that  the  end  of  the 
severed  part  would  not  be  finished  neatly,  but,  with  the  cutting 
edge  at  an  angle,  this  does  not  occur.  This  angle  a  (see  Fig. 
2,  Chapter  VII)  for  different  materials  should  be  about  as 
follows:  For  drill  rod  and  tool  steel,  a  =  10  degrees;  for  Nor- 
way iron  and  machine  steel,  a=  15  degrees;  for  gun  screw 
iron,  a  =  18  degrees;  for  hard  brass,  a  =  20  degrees;  for 
soft  brass  and  copper,  a  =  23  degrees. 


CUTTING-OFF  TOOLS 


93 


The  thickness  of  the  blade  of  a  cutting-off  tool  should  be 
varied  according  to  the  diameter  of  the  work,  the  angle  of  the 
cutting  edge,  and  the  hardness  of  the  material  to  be  operated 
upon.  The  thickness  of  the  blade  of  an  ordinary  circular 
cutting-off  tool  which  is  not  required  to  form  part  of  the 
work  may  be  determined  by  the  following  formula: 


r  = 


D  X  cot  a. 


X  0.14, 


in  which  T  =  thickness  of  blade  in  inches; 
D  =  diameter  of  stock  in  inches; 
a  =  angle  between  cutting  edge  and  axis  of  work. 

When  the  cutting-off  tool  is  also  used  for  forming,  the 
blade  is  shorter  and  the 
thickness  may  be  about 
three-fourths  of  that  ob- 
tained by  the  preceding 
formula.  In  any  case, 
when  a  tapped  hole  passes 
through  the  work,  the  cut- 
ting-off  blade  should  be  wide 
enough  to  remove  the  por- 
tion cut  by  the  chamfered 
end  of  the  tap. 

Rake  of  Forming  and 
Cutting-off  Tools.  —  For  cutting  brass,  the  top  face  of  the 
cutting  part  of  the  tool  is  usually  in  the  same  plane  as  the  axis 
of  the  work,  although,  in  some  cases,  especially  for  soft  brass, 
a  negative  rake  of  about  5  degrees  is  given  the  cutting  edge. 
For  cutting  other  materials,  forming  and  cutting-off  tools  will 
operate  more  satisfactorily  if  given  a  positive  rake.  ^  The  angle 
for  drill  rod  and  tool  steel  should  vary  from  8  to  10  degrees; 
for  gun  screw  iron,  12  degrees;  for  machine  steel,  15  degrees; 
for  Norway  iron,  18  degrees;  for  copper  and  aluminum,  from 
25  to  30  degrees.  For  cutting  steel  and  iron,  the  cutting  edge 
of  the  tool  should  be  at  the  same  height  as  the  center  of  the 
work,  whereas  for  cutting  brass,  bronze,  copper,  and  aluminum, 


Fig.  7.   Box-tool  designed  for 
General  Work 


94 


TOOL  EQUIPMENT 


better  results  are  sometimes  obtained  by  setting  the  cutting 
edge  slightly  above  the  center,  although  for  such  material  as 
Tobin  bronze,  the  cutting  edge  should  be  set  the  same  as  for 
steel. 

Box-tools.  —  Box-tools  are  made  in  a  great  variety  of 
designs  and  types  which  differ  chiefly  in  regard  to  the  number 
and  arrangement  of  the  cutters  and  the  method  of  supporting 
the  part  being  turned.  Most  of  the  types  described  in  the 
following  have  been  extensively  Used.  The  box- tool  shown 
in  Fig.  7  carries  two  cutting  tools.  The  tools  rest  on  a  pin  d 
and  are  held  by  set-screws  a  and  6,  and  by  two  other  set-screws, 


012  i  p 


TT1H 


Machinery,  N.T. 


Fig.  8.   Finishing  Box-tool  largely  used  for  Steel  Work 

not  shown,  which  are  on  the  under  side  of  the  box-tool.  The 
support,  which  is  of  the  V-type,  is  located  at  the  back  of 
the  box-tool  at  an  angle  of  45  degrees  with  the  vertical  center- 
line,  and  is  held  by  the  set-screw  c.  This  box-tool  is  used  for 
general  work,  for  turning  both  one  and  two  diameters,  as 
required.  When  one  diameter  is  being  turned,  the  cutter 
in  the  rear  is  pushed  back. 

In  Fig.  8  is  shown  a  finishing  box-tool  which  is  used  largely 
for  steel  work.  In  this  box-tool,  the  turning  tool  is  held  in 
an  adjustable  block  A  which  is  adjusted  up  and  down  on  the 
body  of  the  holder  by  the  set-screw  B,  and  held  to  the  body 
by  the  cap-screw  C.  A  projection  is  formed  on  the  body  of 
the  box-tool  and  a  corresponding  guiding  groove  is  cut  in  the 
block.  The  turning  tool  is  held  by  means  of  two  set-screws 


BOX-TOOLS 


95 


D  and  the  headless  screws  E.  These  latter  are  for  adjusting 
the  turning  tool,  in  order  to  increase  the  clearance  between 
the  tool  and  the  periphery  of  the  work.  The  V-support  is 
held  in  beveled  grooves  in  the  body  of  the  holder,  by  two 
screws  F  which  pass  through  the  two  parts  of  the  body  sepa- 
rated by  a  saw  cut,  thus  binding  them  together.  The  cutting 
edge  of  the  turning  tool  is  located  from  o.oio  to  0.012  inch 
in  advance  of  the  face  of  the  supports.  A  hole  is  drilled  through 
the  shank  of  the  box-tool  for  holding  a  pointing  tool  or  other 
internal  cutting  tool,  which  is  held  with  the  set-screw  G. 


Fig.  9.    Box-tool  of  the  Roller-support  Type 

In  Fig.  9  is  shown  a  box-tool  of  the  roller-support  type, 
which  is  provided  with  a  roller  support  for  the  front  cutter  and 
a  V-support  for  the  rear  cutter.  The  supports  A  are  held  by 
pins  in  the  two  blocks  B,  which  are  adjusted  in  and  out  by  the 
knurled-head  screws  C.  The  blocks  B  are  held  to  the  body  of 
the  box- tool  by  cap-screws  which  are  tapped  into  them.  A 
slot  is  cut  in  the  body  of  the  holder  in  which  the  bodies  of 
the  cap-screws  slide,  thus  providing  adjustment  for  turning 
different  diameters. 

A  simple  type  of  shaving  box-tool  is  shown  at  B  in  Fig.  10. 
This  tool  is  provided  with  V-supports  which  are  adjusted  by 


96 


TOOL    EQUIPMENT 


the  collar-head  screw  e  and  are  clamped  in  position  by  means 
of  the  clamp  bolts  /.  The  turning  tool  g  is  adjusted  by  a  collar- 
head  screw  h  and  is  held  in  position  by  a  set-screw  i.  This  tool 


Fig.  10.    Roller  Steadyrest  —  Shaving  and  Roughing  Box-tools 

is  of  very  simple  construction  and  is  used  where  only  one 
diameter  is  to  be  turned  at  a  time. 

The  roughing  box-tool  C,  Fig.  10,  is  provided  with  roller 
supports,  and  the  turning  tool  j  is  held  in  a  square  hole  pro- 
vided in  the  stud  k;  this  stud  clamps  the  turning  tool  against 
the  face  of  the  box-tool  holder.  Adjustment  for  height  is 


BOX-TOOLS 


97 


secured  by  means  of  the  set-screw  /.     Two  set-screws,  one  of 
which  is  shown  at  m,  act  as  an  adjustment  for  stud  k. 

The  box- tool  shown  at  A  in  Fig.  n  holds  three  turning 
tools,  and  can  also  carry  a  centering  tool  or  drill,  which  is  held 
in  the  shank  of  the  holder.  The  flat  base  a  has  two  grooves 


11. 


Multiple  Turning  Tool,  Adjustable  Hollow  Mill, 
and  Standard  Three-tool  Box-mill 


extending  its  full  length,  in  one  of  which  the  three  holders  b 
for  the  cutting  tools  are  held,  and  in  the  other  two  the  brackets 
c  for  roller  supports.  This  box-tool  can  be  used  for  turning 
three  different  diameters  at  one  setting  and  is  used  either  for 
roughing  or  finishing  cuts.  The  roller  supports  may  be  ad- 
justed to  lead  or  follow  the  cutting  tools  by  simply  moving 
them  along  the  slot  in  the  holder.  The  brackets  carrying  the 


98  TOOL  EQUIPMENT 

supports  can  be  placed  in  any  desired  position  and  the  holders 
for  the  cutting  tools  can  also  be  adjusted  to  suit  the  various 
diameters  and  lengths  of  shoulders  on  the  work. 

An  adjustable  type  of  " hollow  roughing  mill"  or  box- tool 
is  shown  at  B  in  Fig.  u.  This  is  supplied  with  two  cutter 
heads,  each  containing  four  cutters  d.  The  flat  arm  e  of  the 
box-tool  has  a  spline  cut  the  full  length,  and  also  a  slot  through 
which  the  studs  of  the  cutter  heads  pass.  The  studs  are  made 
integral  with  the  cutter  heads  and  are  clamped  by  nuts  as 
shown.  The  four  cutters  in  each  head  are  adjusted  by  re- 
moving the  head  from  the  arm  and  placing  it  on  a  stand 
fitted  with  a  plug  gage  of  the  same  diameter  as  the  work  to 
be  turned.  This  stand  holds  the  cutter  head  in  the  correct 
relation  to  the  plug  gage,  so  that  the  tools  can  be  brought 
into  contact  with  the  plug  gage  and  then  clamped.  This  tool 
which  is  adapted  to  rough  turning  cast  iron  is  supplied  with 
a  hole  in  the  shank  for  holding  a  centering  tool  or  drill.  The 
heads  for  the  cutters  are  adjustable  along  the  body  of  the 
holder. 

The  box- tool  shown  at  C  in  Fig.  n  is  of  the  open- type  con- 
struction and  is  supplied  with  one  turning  tool  clamped  to 
its  face,  the  work  being  supported  at  this  point  by  roller 
supports.  The  second  tool,  which  is  set  at  an  angle  and  held 
down  by  a  heel  clamp,  can  be  used  for  turning  a  second  di- 
ameter; the  work  is  supported  opposite  this  tool  by  a 
V-support. 

Box-tools  of  Over-cut  Type.  —  The  type  of  box-tool  com- 
monly used  on  the  "Acme"  multiple-spindle  automatic  is 
known  as  the  over-cut  type;  this  usually  carries  two  cutting 
tools  as  shown  in  Fig.  12.  The  front  cutting  tool  is  set  "tan- 
gentially"  to  the  work,  while  the  rear  cutter  is  radial  in  rela- 
tion to  the  center  of  the  work.  The  front  tool,  when  used  for 
taking  a  finishing  cut,  is  set  about  o.oio  inch  in  advance  of 
the  supports  and  is  ground  a  little  high  at  the  rear  to  provide 
for  clearance.  The  roller  supports  c  which  are  commonly 
used  are  shown  dismantled  at  D  and  fastened  to  the  holders 
at  E.  The  support  holders  are  held  to  the  box-tool  body  by 


BOX-TOOLS 


99 


a  cap-screw  e  and  are  backed  up  by  large-headed  screws  /. 
The  rear  cutting  tool  h  is  held  in  a  tool-holder  which  is  retained 
in  a  V-groove  in  the  body  of  the  box-tool  by  a  cap-screw  k 
and  is  provided  with  an  elongated  slot  for  adjustment. 

The  box- tool  shown  at  H  is  known  as  a  "round  box- tool" 
because  of  the  rounded  shape  of  its  body.  It  is  provided  with 
a  solid  support  which  is  very  rarely  used  except  on  small  brass 
work.  It  is  particularly  suited  for  use  in  the  "first"  position 
when  the  forming  cut  overlaps  the  box-tool  cut.  This  type 


Fig.  12.   Group  of  Over-cut  Box- tools  used  on  the  "Acme"  Mul- 
tiple-spindle Automatic  Screw  Machines 

of  box-tool  is  also  provided  with  roller  supports  for  general 
work. 

Spring-releasing  Box-tool.  —  The  regular  box-tool,  when 
used  for  taking  heavy  roughing  cuts,  usually  leaves  a  spiral 
mark  on  the  work  in  backing  off.  This  is  due  to  the  extreme 
point  of  the  cutting  tool  becoming  heated,  and  a  certain 
amount  of  the  cuttings  sticking  to  it,  thus  forming  a  ragged 
edge,  which  produces  an  objectionable  mark  on  the  work  when 
the  tool  is  withdrawn.  To  overcome  this  difficulty,  the 
National-Acme  Mfg.  Co.  designed  the  "spring-releasing  box- 
tool"  illustrated  in  Fig.  13.  In  this  design,  the  front  cutting 
tool  is  removed  from  the  work  on  the  back  stroke,  and  is  thus 


100 


TOOL  EQUIPMENT 


prevented  from  producing  an  objectionable  mark.  The  front 
part  of  the  body  A  is  cut  out  as  shown,  and  a  block  C  is  held 
to  it  by  a  bolt  and  nut.  This  block  is  provided  with  a  tongue 
so  that  it  is  adjustable  in  a  vertical  direction  on  the  face  of 
the  box-tool  body.  The  tool-holder  B  is  provided  with  an 
angular  groove  which  fits  over  a  corresponding  tongue  on  the 
face  of  the  block  C.  The  tool-holder  is  held  to  block  C  by  a 
shouldered  screw  E,  the  diameter  of  which  is  smaller  than 
the  elongated  hole  in  the  tool-holder,  to  provide  for  a  slight 
movement.  .  Screw  E  is  backed  up  by  headless  screw  F  to 


POSITION  OF  TOOL' 
WHEN  CUTTING 


POSITION  OF  TOOL 
WHEN  RELEASED 


Machinery 


Fig.  13.   Spring-releasing  Type  of  Box-tool 

prevent  it  from  loosening  when  the  tool-holder  is  moved  back 
and  forth  on  it. 

In  the  tool-holder  B,  there  is  a  spiral  spring  H  which  acts 
on  a  plunger,  the  latter  bearing  against  the  body  of  the  shoul- 
dered screw  E.  The  action  of  this  spring  draws  the  tool- 
holder  forward  toward  the  center-line  of  the  box-tool  body, 
its  movement  being  stopped  by  the  headless  screw  G.  The 
tool-holder  B  works  on  a  tongue  which  is  at  an  angle  with  the 
line  X  Y.  When  the  front  cutting  edge  of  the  tool  strikes 
the  work,  it  compresses  the  coil  spring  //,  forcing  the  tool- 
and  holder  back  until  its  movement  is  stopped  by  the  shoul- 
dered screw  E.  Then  when  the  main  tool-slide  stops  advancing 


BOX-TOOLS 


IOI 


and  begins  to  retreat,  the  pressure  on  the  cutting  tool  is  re- 
leased, allowing  the  spring  to  force  the  tool-holder  up  on  the 
angular  tongue  and  thus  raise  the  tool  from  the  work  as  shown 
by  the  diagrams  at  the  lower  part  of  the  illustration.  The 
block  C  carrying  the  tool-holder  is  adjusted  vertically  for 
turning  different  diameters  by  means  of  the  collar-head  screw  /. 
The  roller  supports  are  held  in  holders  /  which  are  backed 
up  by  blocks  K\  these  blocks  are  held  in  place  by  a  cap-screw 


Fig.  14.   Turning  Tool  for  Taper  or  Irregular  Shapes 

M  and  drilled  out  to  receive  a  headless  screw  Ly  the  latter 
forming  a  heel  on  which  the  rear  part  of  the  block  rests.  As 
the  diameter  of  the  work  increases,  the  screw  M  is  released, 
allowing  the  roller-support  holders  /  to  drop  back  to  bring 
the  rolls  to  the  proper  position.  Then  the  screw  L  is  brought 
out  until  the  block  K  is  practically  in  a  parallel  position, 
when  the  screw  M  is  tightened. 

Taper-turning  Box-tool.  —  The  box-tool  shown  in  Fig.  14, 
which  is  adapted  to  the  turning  of  taper  or  irregular  forms, 
is  held  by  a  shank  in  the  turret  of  the  machine  and  is  supplied 


102 


TOOL  EQUIPMENT 


with  a  bushing  on  the  front  end  which. guides  the  work.  The 
circular  slide  A  carries  the  turning  tool  B  and  is  fitted  with 
a  pin  C  which  comes  in  contact  with  the  adjustable  guide  D 
held  on  the  cross-slide.  When  the  turning  operation  is  com- 
pleted, the  cross-slide  recedes,  allowing  a  spring  located  inside 
the  holder  to  move  the  slide  A  back  to  its  original  position. 
The  guide  D  held  on  the  holder  E  which  is  attached  to  the 
cross-slide  can  be  made  of  any  shape,  so  that  any  irregular 
form  as  well  as  tapered  work  can  be  secured.  This  guide  is 


Fig.  15.  Taper-turning  Tool 

fulcrumed  on  a  pin  in  the  bracket  and  is  supported  and 
adjusted  by  two  set-screws.  This  tool  is  used  on  the  Cleveland 
automatics. 

A  taper- turning  tool  made  by  the  Brown  &  Sharpe  Mfg.  Co., 
and  one  that  is  recommended  for  accurate  work,  is  shown  in 
Fig.  15.  When  in  operation,  a  block  or  plate,  which  can  be 
set  at  any  angle  desired,  presses  on  the  point  of  screw  a,  which 
forces  the  holders  carrying  the  supports  and  turning  tool 
out  from  the  center.  The  screw  a  is  tapped  into  sleeve  b  and 
moves  the  latter  in  the  direction  of  the  arrow.  Now  as  the 
sleeve  b  is  forced  in,  it  pulls  on  the  band  spring  c,  which  is 
attached  to  the  circular  block  d,  thus  turning  the  latter  around 
in  the  direction  of  the  arrow.  The  spring  is  fastened  in  a  slot 
cut  in  the  circular  block  d.  The  circular  block  d  has  eccentric 
projections  e  formed  on  it,  which  fit  in  slots  cut  in  the  tool- 
holder  /  and  support-holders  g.  As  the  sleeve  b  is  forced  in, 


BOX-TOOLS 


I03 


it  carries  the  spring  c  forward,  thus  rotating  the  circular  block 
d  in  the  direction  of  the  arrow  and  forcing  the  holders  carry- 
ing the  supports  and  turning  tools  out  from  the  center. 

In  the  end  view  shown  at  A,  the  turning-tool  and  support- 
holders  are  shown  in  the  position  they  occupy  before  screw  a 
engages  the  operating  block.  The  supports  and  turning 
tool  can  be  adjusted  independently  of  each  other  by  the  set- 


Machinery 


Fig.  16.   Various  Methods  of  Applying  Box-tool  Cutters  to  the  Work 

screws  h,  and  are  held  by  the  screws  i.  After  the  turret  drops 
back,  disconnecting  the  screw  a  from  the  block,  the  turning 
tool  and  supports  are  returned  to  their  former  position  by 
means  of  the  coil  springy  (shown  at  B).  The  spring  j  presses 
against  a  pin  k  (shown  at  C)  which  is  riveted  to  a  plate  /;  this 
plate  is  held  to  the  shank  of  the  holder  by  a  pin  fitting  in  a 
slot.  Plate  /  is  held  up  against  the  outer  casing  of  the  holder 
by  the  nut  w,  screwed  onto  the  shank  of  the  holder. 


104  TOOL  EQUIPMENT 

Methods  of  Applying  Box-tool  Cutters.  —  Box-tool  cutters 
are  applied  to  the  work  either  radially  as  shown  at  A,  Fig.  16, 
or  tangentially  as  illustrated  at  B  and  C.  The  radial  position 
for  the  cutter  is  more  commonly  used  for  brass  work,  whereas 
the  tangential  cutter  is  used  for  all  classes  of  steel  work,  and 
also  for  brass  work  in  some  cases.  The  cutting  edge  of  a  radial 
cutter  is  set  above  the  horizontal  center-line  of  the  work  an 
amount  that  is  usually  about  0.02  times  the  diameter  which 
is  being  turned.  This  is  the  preferable  method  of  applying  the 
turning  tool  for  taking  roughing  cuts  on  brass  rods.  If  the 
stock  is  rough  or  of  irregular  shape,  the  cutter  should  precede 
the  support  an  amount  varying  from  o.oio  to  0.020  inch,  but, 
if  the  bar  is  cylindrical  and  has  a  finished  surface,  the  sup- 
port, when  taking  roughing  cuts,  should  precede  the  turning 
tool,  as  shown  by  the  dotted  lines  at  A .  The  tangential  cutter 
shown  at  B  is  set  to  take  a  roughing  cut  from  a  bar  having  a 
comparatively  rough  surface.  The  tangential  cutter  shown 
at  C  is  set  for  taking  a  finishing  cut  in  steel.  The  cutting  edge 
is  located  back  of  the  center  of  the  work  an  amount  equal  to 
o.io  of  the  diameter  d,  being  turned.  For  cutting  brass,  the 
tangential  cutter  is  set  in  line  with  the  center,  or,  in  some 
cases,  slightly  in  advance  of  the  center. 

A  method  of  applying  two  turning  tools  for  roughing  down 
steel  work  is  shown  at  D,  and  at  E  three  turning  tools  used 
for  the  same  purpose.  For  taking  roughing  cuts  on  brass, 
where  considerable  material  is  to  be  removed,  a  hollow  mill 
is  generally  used,  but  the  method  shown  at  D  can  sometimes 
be  employed  to  advantage.  At  E  no  supports  are  used,  as  the 
tools  support  the  stock.  These  tools  can  either  be  set  radially 
as  shown,  and  a  slight  amount  in  advance  of  each  other,  or 
tangentially  and  at  varying  heights,  so  as  to  distribute  the 
cuts  equally  among  the  tools.  For  taking  roughing  cuts  on 
steel,  it  is  preferable  to  set  the  cutters  tangentially  to  the 
work. 

At  F  is  shown  a  method  of  applying  two  tangential  turning 
tools  for  turning  down  two  diameters  on  a  piece  of  work. 
This  method  is  used  when  the  distance  a  is  not  much  greater 


iff 

£-4*1  I      1 1  '•  b 


106  TOOL  EQUIPMENT 

than  from  J  to  f  inch.  For  a  larger  dimension  a,  it  is  generally 
advisable  to  use  two  separate  box-tools,  provided  there  is 
sufficient  room  in  the  turret.  When  turning  tools  are  used  in 
this  manner,  the  thickness  b  of  the  first  tool  should  be  such 
that  the  second  tool,  when  set  tightly  against  the  first  one,  will 
turn  the  shoulder  to  the  desired  length.  To  illustrate,  assume 
that  a  =  0.375  incnJ  £  =  10  degrees;  then  b  =  a  X  cos 
j8  =  0.375  X  0.9848  =  0.369  inch.  When  two  turning  tools 
are  used  in  this  manner,  they  should  be  ground  on  all  sur- 
faces and  should  also  be  made  a  good  fit  in  the  square  or 
oblong  hole  cut  in  the  body  of  the  holder  to  receive  them. 

Holding  and  Adjusting  Box-tool  Cutters.  —  At  A  in  Fig.  17 
is  shown  a  method  which  is  commonly  used  for  holding  a  box- 
tool  cutter  for  brass  work.  A  square  hole  is  cut  in  the  body 
of  the  holder  to  receive  the  cutter,  the  latter  being  held  by  a 
set-screw  a.  The  cutter  is  adjusted  for  different  diameters 
by  the  collar-head  set-screw  b  which  bears  against  the  rear 
end  of  the  tool.  By  cutting  a  slot  in  the  turning  tool  to  fit  the 
collar  on  the  screw,  this  screw  may  be  used  for  adjusting  the 
tool  both  in  and  out. 

The  method  shown  at  B  for  holding  the  turning  tool  is 
used  particularly  for  brass  work.  The  turning  tool  is  held  in 
the  block  c  by  two  set-screws  d,  the  block  being  adjustable 
along  the  body  of  the  holder.  The  block  c  has  a  projecting 
shank  which  passes  through  the  body  of  the  holder  and  is 
fastened  to  it  by  means  of  the  nut  and  washer  shown.  This 
method  of  holding  the  tool  is  very  convenient  for  certain 
classes  of  work,  especially  when  different  diameters  are  re- 
quired, as  it  is  possible  to  have  one  or  more  blocks  for  holding 
the  turning  tools. 

A  method  of  adjusting  and  holding  a  tangential  cutter  is 
shown  at  C.  The  cutter  is  set  at  an  angle  from  the  face  of  the 
box-tool,  and  is  held  in  the  body  of  the  holder  by  two  set- 
screws  e  and  /.  The  tool  rests  on  a  small  block  /i,  thus  allow- 
ing it  to  be  adjusted  for  turning  different  diameters,  the  two 
set-screws  being  used  in  connection  with  this  block  for 
adjusting. 


BOX-TOOLS  107 

A  method  of  holding  the  turning  tool  somewhat  similar  to 
that  just  described  is  shown  at  D.  The  tool  rests  on  the  body 
of  a  screw  g  instead  of  on  a  block.  These  two  methods  of 
adjusting  the  tool  can  only  be  used  for  certain  classes  of  work. 
A  method  which  allows  of  more  adjustment  is  shown  at  E. 
The  tool  is  adjusted  and  held  by  three  set-screws,  thus  allow- 
ing it  to  be  adjusted  for  various  diameters,  with  the  face  of 
the  tool  held  in  a  place  parallel  to  the  horizontal  center-line. 

The  methods  shown  at  C,  D,  and  E  are  used  principally  for 
roughing  box- tools.  At  F  is  shown  the  method  of  adjusting 
the  turning-tool  holder  which  is  usually  applied  to  finishing 
box-tools.  The  tool  is  held  in  a  block  h,  which  is  adjusted  up 
and  down  on  the  body  of  "the  holder  by  means  of  set-screw  i\ 
the  block  is  held,  when  in  the  desired  position,  by  cap-screw/. 
This  block  has  a  groove  in  it  which  fits  on  a  tongue  formed 
on  the  box-tool  body,  thus  holding  the  tool-holder  rigidly. 
At  G  is  shown  a  method  similar  to  that  just  described,  but  the 
turning  tool  is  held  in  the  holder  in  a  manner  similar  to  that 
shown  at  C.  By  this  means,  the  cutter  may  be  set  at  a  slight 
angle  from  the  horizontal  center-line,  thus  giving  it  more 
clearance,  as  is  sometimes  necessary,  especially  when  cutting 
steel.  A  slight  adjustment  of  the  tool,  independently  of  the 
tool-holder,  is  also  possible. 

With  the  design  shown  at  H  and  7,  a  micrometer  screw  is 
used  for  setting  the  box-tool  cutter  to  the  correct  diameter. 
This  micrometer  screw  k  has  two  shoulders  and  is  screwed 
into  the  body  of  the  holder,  the  body  of  the  screw  being  made 
a  good  fit  in  the  block  shown  in  detail  at  /.  A  4o-pitch  thread 
is  cut  on  this  screw,  so  that  for  one  revolution  of  the  screw  the 
turning  tool  is  moved  a  distance  equal  to  0.025  inch.  The 
block  is  held  to  the  body  of  the  holder  in  the  same  manner 
as  that  shown  at  F  and  G. 

A  good  method  of  holding  two  or  more  turning  tools  for 
roughing  is  shown  at  /,  the  holder  being  made  with  the  desired 
number  of  projecting  lugs  or  tool-holders  m.  The  tool  is  held 
in  a  stud  n,  which  has  a  square  hole  cut  in  it  to  receive  the 
tool.  This  hole  is  cut  at  an  angle  with  the  face,  so  that  the  tool 


io8 


TOOL  EQUIPMENT 


is  set  at  the  desired  angle.  Two  set-screws  o  are  used  to  pre- 
vent the  tool  from  turning  under  the  pressure  of  the  cut,  and 
also  to  permit  of  a  slight  adjustment  of  the  tool.  This  method 
of  holding  a  turning  tool  is  used  mostly  for  roughing  work. 

Box-tool  Work  Supports.  —  The  type  of  support  to  use  and 
the  method  of  applying  it  are  governed  largely  by  the  follow- 
ing conditions:  Shape  of  the  stock,  whether  round  or  other- 
wise; character  of  the  cut,  whether  taper  or  otherwise;  na- 
ture of  the  material,  whether  soft  or  hard;  number  of  different 
diameters  to  be  turned;  length  of  the  work  being  turned; 


Machinery,  N.Y. 


Fig.  18.   Methods  of  Applying  Box-tool  Supports  to  the  Work 

clearance  allowable  between  the  face  of  the  circular  form  tool 
and  the  box-tool. 

At  A  in  Fig.  18  is  shown  a  box-tool  support  used  in  rough- 
ing box-tools.  This  support  surrounds  the  work  and  precedes 
the  turning  tool.  It  is  used  mainly  for  turning  down  cylindrical 
work  in  which  the  finished  diameter  is  to  be  concentric  with 
the  part  which  is  not  finished,  that  is,  which  has  not  had  a 
cut  taken  from  it.  Where  the  work  being  turned  projects 
more  than  five  times  its  diameter  from  the  chuck,  and  is  of  large 
diameter,  it  is  not  advisable  to  use  a  bushing  support,  unless 
the  stock  is  reduced  by  the  circular  cut-off  tool,  in  order  to 
weaken  it  somewhat. 

At  B  is  shown  a  support  which  is  sometimes  used  for  finish- 


BOX-TOOLS  109 

ing  box-tools.  One  objection  to  the  design  is  that  as  it  does 
not  surround  the  work,  a  bar  of  larger  radius  than  the  sup- 
porting surface  is  deflected  to  one  side,  thus  producing  work 
which  is  not  straight,  but  slightly  tapered.  The  support  shown 
at  C  is  commonly  called  a  UV- support,"  and  has  a  two-point 
bearing  on  the  work.  The  thrust  from  the  tool  is  against 
both  supports.  As  a  rule,  this  support  should  not  precede  the 
cutting  tool,  for  the  reason  that,  if  the  work  is  not  cylindrical 
in  shape,  the  irregularities  of  the  bar  will  be  reproduced  on  the 
work  that  is  turned.  This  V-support  can  be  used  for  brass, 
steel,  and  similar  materials,  and  gives  satisfactory  results  when 
it  does  not  precede  the  turning  tool. 

In  turning  cast  iron  or  aluminum,  difficulty  is  sometimes 
encountered  in  producing  a  finished  surface  on  the  work. 
This  is  usually  due  to  fine  chips  or  dust  becoming  wedged  in 
between  the  supports  and  the  work,  thus  causing  an  abrasive 
action  which  roughens  the  work.  It  is,  therefore,  advisable 
when  turning  aluminum  or  cast  iron,  to  use  roller  supports. 
One  method  of  applying  the  roller  supports  is  shown  at  D. 
These  rollers  should  be  hardened  and  ground,  and  it  is  usually 
preferable  to  lap  them  also,  so  that  they  are  very  smooth. 
This  support  is  also  used  when  turning  machine  steel,  and  is 
made  to  bear  rather  hard  against  the  work,  which  gives  it  a 
burnished  appearance.  Another  support  which  is  sometimes 
used  for  cast  iron  is  shown  at  E.  This  gives  a  two-point  bear- 
ing, and  allows  the  tool  to  be  set  radially  to  the  work.  This 
support,  however,  is  not  as  good  as  the  roller  type. 

At  F  is  shown  a  method  of  supporting  the  work  when  apply- 
ing two  turning  tools  to  it.  This  method  is  used  principally 
for  roughing  down  steel  work  and  also  when  it  is  necessary 
to  rough  down  the  work  from  a  large  to  a  small  diameter  in 
the  least  possible  time.  As  a  rule,  supports  for  box-tools  should 
be  made  from  high-carbon  steel,  left  glass-hard,  and  given  a 
very  smooth  finish,  which  is  one  of  the  chief  requirements  of 
a  box-tool  support. 

Holding  and  Adjusting  Box-tool  Supports.  —  Various 
methods  of  holding  and  adjusting  box-tool  supports  are  shown 


no 


TOOL  EQUIPMENT 


in  Fig.  19.  At  A  is  shown  a  common  method  of  holding  a 
bushing  support.  The  support  shown  at  B  is  tongued  to  the 
holder  and  is  adjustable  in  an  axial  direction.  At  C  is  shown 
one  method  of  holding  a  V-support.  A  rectangular  hole  is 
cut  in  the  body  of  the  holder  in  which  the  supports  fit.  When 
in  position,  the  supports  are  held  by  the  set-screw  b.  This 
method  of  holding  a  V-support  is  commonly  used  for  both 
roughing  and  finishing  box-tools,  when  one  cutting  tool  is 


H    Machinery 


Fig.  19.   Methods  of  Holding  and  Adjusting  Box-tool  Supports 

applied  to  the  work,  and  sometimes  when  two  cutting  tools 
are  used  so  close  together  that  it  is  only  necessary  to  support 
the  work  at  one  place.  At  D  is  shown  a  method  of  holding  a 
V-support  when  it  is  necessary  to  apply  more  than  one  sup- 
port to  the  work,  as  when  turning  down  to  more  than  one 
diameter  at  a  time.  This  support  is  held  in  a  movable  block  c, 
which  is  adjusted  along  the  body  of  the  holder.  These  last 
two  methods  are  principally  for  box-tools  used  for  turning 
brass  or  a  similar  class  of  materials,  in  which  the  cutter  is 
set  radially  to  the  work.  At  E  is  shown  a  common  method  of 


BOX-TOOLS  III 

applying  the  V-support  to  a  box-tool  used  for  cutting  steel. 
This  method  is  used  when  the  cutting  tool  is  set  tangentially. 
The  methods  shown  at  C,  D,  and  E  are  limited  in  their  scope, 
to  a  certain  extent,  owing  to  the  fact  that  they  cannot  be  used 
in  conjunction  with  a  circular  form  tool  when  it  is  necessary 
to  have  the  box-tool  work  closer  to  the  forming  tool  than  the 
thickness  of  the  web  e.  For  this  class  of  work,  the  design 
shown  at  F  is  commonly  used.  This  support  is  beveled  and 
set  in  a  beveled  slot  cut  in  the  front  end  of  the  box-tool  body. 
The  body  of  the  holder  is  split  and  screws  bind  the  two  parts 
together. 

At  G  is  shown  a  method  of  applying  roller  supports.  These 
roller  supports  are  held  in  two  movable  members,  /  and  g, 
which,  in  turn,  are  fastened  to  the  body  of  the  holder  by  the 
clamping  screw  h.  As  the  clamping  screw  h  would  not  be 
sufficient  to  hold  these  roller-support  holders  against  the 
pressure  of  the  cut,  they  are  held  in  the  correct  position  by 
large-headed  screws  i,  which  are  screwed  into  the  body  of  the 
holder.  At  H  is  shown  another  method  of  applying  roller 
supports.  In  this  case,  the  supports  are  held  on  two  sliding 
holders,  j  and  k,  which  slide  in  grooves  cut  in  the  box- tool 
body.  They  are  adjusted  in  and  out  to  the  required  diameter, 
and  are  held  by  the  clamping  screws.  There  are  numerous 
other  methods  of  holding  roller  supports,  but  they  are  all  of 
a  somewhat  similar  character  to  those  already  shown.  Natu- 
rally, there  are  various  conditions  which  govern  the  method  of 
applying  these  supports.  The  methods  of  holding  supports, 
previously  described,  are  those  generally  used  in  standard 
box-tools,  and  do  not  include  those  used  for  special  conditions. 
Design  H  is  preferable  usually  to  the  one  shown  at  G. 

Cutting  Angles  for  Box-tool  Cutters.  —  It  is  not  sufficient 
to  hold  a  box-tool  cutter  rigidly  and  support  the  work  well, 
to  obtain  good  results,  but  it  is  also  necessary  to  have  sufficient 
clearance,  and  the  correct  cutting  angle  on  the  tool.  The  tool 
must  have  sufficient  clearance  and  rake,  so  as  to  remove  the 
material  with  the  least  possible  resistance  and  power.  The 
manner  in  which  the  tool  is  applied  to  the  work,  and  the  ma- 


112  TOOL  EQUIPMENT 

terial  on  which  it  operates  govern  the  cutting  angle  on  the  tool. 
Generally,  in  automatic  screw  machine  practice,  the  cutter 
is  set  radially  for  turning  brass  and,  when  held  in  this  way, 
the  cutting  angles  are  approximately  as  illustrated  in  Fig.  20. 
Tool  A  is  for  roughing  and  tool  B  for  finishing,  the  cutting 
face  of  the  latter  being  ground  parallel  for  a  short  distance 
y  equal  to  approximately  one-fifth  of  the  diameter  being  turned. 
For  steel  turning,  the  cutter  should  be  set  tangentially  to  the 
work  as  shown  at  C  and  D.  The  end  of  tool  C  should  be  ground 
to  approximately  the  following  angles: 

Cutting  Angles  for  Machine  Steel  Cutting  Angles  for  Tool  Steel 
a  =10  degrees;  a  =  8  degrees; 

6  =  10  degrees;  b  =  8  degrees; 

c=8  to  10  degrees;  c. =  8  to  10  degrees; 

d=  70  to  72  degrees.  d=?2  to  74  degrees. 

The  form  of  tool  shown  at  C  is  commonly  used  for  roughing 
cuts,  but  will,  not  produce  an  absolutely  square  shoulder. 
For  finishing  cuts,  the  tool  is  ground  as  shown  at  D,  which 
produces  a  square  shoulder.  The  cutting  angles  for  tool  D 
are  as  follows: 

Cutting  Angles  for  Machine  Steel  Cutting  Angles  for  Tool  Steel 
e  =from  10  to  12  degrees;  e  =from  8  to  10  degrees; 

/  =from  15  to  1 8  degrees;  /  =  from  8  to  10  degrees; 

g  =  from  60  to  65  degrees.  g  =  from  70  to  74  degrees. 

While  the  cutting  face  on  the  tool  shown  at  D  is  straight, 
it  is  usually  advisable,  especially  when  cutting  machine  steel 
and  Norway  iron,  to  give  more  "lip"  to  the  tool,  as  shown  by 
the  dotted  line  h.  The  cutting  edge  of  a  radial  cutter  for  rough- 
turning  brass  rod  is  set  above  the  horizontal  center  line  of  the 
work,  an  amount  equal  to  about  0.02  times  the  diameter  being 
turned.  If  the  stock  is  rough  or  of  irregular  shape,  the  cutter 
should  precede  the  support  by  an  amount  equal  to  from  o.oio 
to  0.020  inch,  but,  when  the  bar  is  cylindrical  and  has  a  fin- 
ished surface,  the  support  for  roughing  cuts  should  precede  the 
tool.  The  face  of  a  tangent  cutter  should  be  set  back  a  distance 
x  (see  Fig.  20  D)  equal  to  about  one-eighth  the  diameter  being 
turned,  for  tool  steel,  and  one-tenth  the  diameter,  for  machine 


HOLLOW  MILLS 


steel.  Sometimes,  it  is  also  advisable,  especially  when  cutting 
machine  steel,  to  elevate  the  tool  from  the  horizontal  an  angle 
of  from  i  to  2  degrees,  to  increase  the  clearance. 

Size  of  Steel  for  Box-tool  Cutters.  —  For  special  conditions, 
the  tool  is  sometimes  made  of  rectangular  section,  but  ordi- 


J 1 t  V 


Eig.  20.   Different  Methods  of  Applying  Box-tool  Cutters  in  Automatic 
Screw  Machine  Practice 

narily  square  stock  is  used.    The  square  sections  recommended 
for  box-tool  cutters  are  as  follows: 

Largest  diameter  of  work,  in  inches:   5      f     \      f      i 
Square  section  of  tool,  in  inches:         T\     \     T\     f     T\ 

Roller  Steadyrest.  —  A  simple  steadyrest  of  the  roller- 
support  type  is  shown  at  A  in  Fig.  10.  The  roller  supports  a 
are  held  in  slides  b  which  are  adjusted  by  means  of  screws  c. 
The  slides  are  then  clamped  in  the  desired  position  by  means 
of  the  clamp  bolts  d.  This  steadyrest  may  be  used  to  support 
the  end  of  a  bar  when  using  exceptionally  wide  forming  tools, 
when  knurling,  or  for  centering  the  end  of  the  stock  by  insert- 
ing a  suitable  tool  in  the  shank. 

Hollow  Mills.  —  For  roughing  cuts,  especially  in  brass,  a 
hollow  mill  gives  satisfactory  results.  A  form  which  is  com- 


TOOL  EQUIPMENT 


monly  used  in  connection  with  automatic  screw  machine  work 
is  shown  in  Fig.  21,  which  includes  the  angles  of  the  cutting 
edges  for  turning  various  materials.  The  hole  in  the  center 
of  the  hollow  mill  should  have  a  taper  of  from  f  to  yV  inch  per 
foot  to  provide  clearance.  The  cutting  edge  of  a  mill  to  be 
used  on  steel  should  be  set  about  one-tenth  of  the  diameter 
ahead  of  the  center,  whereas,  if  the  mill  is  to  be  used  on  brass, 
the  cutting  edge  should  be  on  the  center-line.  Hollow  mills 
of  the  inserted-blade  type  are  also  used  to  some  extent  on 


./TAPER  X'TOJJ"PER  FOOT        /FLAT 


Machinery 


Angle  as  Shown 
by  Illustration 


Angles  of  Cutting  Edges,  in  Degrees, 
for  Different  Materials 


Brass  Rod 


Machine  Steel 


Tool  Steel 


10 
3 


Fig.  21.   Hollow  Mill  and  Angles  of  Cutting  Edges 

automatic  screw  machines,  although  they  are  more  extensively 
employed  on  screw  machines  of  the  hand  type. 

Centering  and  Facing  Tools.  —  When  drilling  holes  which 
are  less  than  7%  inch  in  diameter,  it  is  always  advisable,  es- 
pecially when  the  hole  passes  through  the  work,  to  use  a  start- 
ing or  centering  tool.  At  A  in  Fig.  22  is  shown  a  centering 
tool  which  is  used  for  brass  work,  and  at  B,  one  which  is  used 
for  steel  and  soft  iron.  This  latter  tool  is  similar  to  the  or- 
dinary twist  drill,  except  that  the  flutes  are  shorter.  A  worn- 
out  twist  drill  is  sometimes  used  for  this  purpose,  with  the 


CENTERING   AND    FACING   TOOLS 


point  ground  thin,  as  shown  at  a,  which  reduces  the  pressure 
and  allows  the  drill  to  start  easier.  This  tool  also  makes  a 
better  center  than  would  a  drill  with  a  thicker  point.  The 
included  angle  of  the  cutting  edges  on  a  centering  tool  should 
be  less  than  the  drill  which  is  to  follow.  If  this  is  not  the 
case,  the  point  of  the  drill  will  start-  to  cut  before  the  body  of 
the  drill  is  properly  supported;  consequently,  an  imperfect 
center  will  be  formed.  If  an  imperfect  center  has  been  formed, 
the  drill  will  run  out,  as  shown  at  C. 

It  is  practically  impossible  for  a  drill  to  start  concentric  with 
the  center  of  the  work  when  a  small  teat,  as  shown,  has  been  left 
by  the  centering  tool,  unless  the  latter  has  a  more  acute  angle 


•  90°TO  100° 


90  TO  100° 


'ACE  OF 
DRILL  HOLDER 


Fig.  22.   Centering  Tools —  Starting  the  Drill  Concentric 

than  the  drill  to  follow,  when  there  is  no  difficulty  (see  diagram 
D).  The  included  angle  of  the  point  for  centering  tools  varies 
from  90  to  100  degrees;  90  degrees  should  be  used,  preferably, 
for  brass,  and  100  degrees  for  steel.  The  included  angle  of 
the  point  of  the  drill  varies  from  118  to  120  degrees,  118  degrees 
being  generally  used. 

At  A  in  Fig.  23  is  shown  a  common  form  of  centering- tool 
holder.  This  tool  holder  has  been  found  very  successful  for 
general  conditions  when  the  work  has  been  gaged  to  length 
by  a  stop,  thus  obviating  the"  necessity  of  using  a  facing  tool. 
It  is  provided  with  a  split  bushing  a,  or  is  made  without  the 
bushing,  the  hole  for  the  centering  tool  simply  passing  through 
the  body  and  the  shank,  and  being  of  the  same  diameter  as 
the  centering  tool.  At  B  is  shown  a  combination  centering 


n6 


TOOL  EQUIPMENT 


and  facing  tool.  This  tool  is  used  when  the  stop  for  gaging 
the  work  to  length  has  been  dispensed  with,  the  tool  b  being 
used  for  facing  the  work  to  the  required  length.  At  C  is  shown 
a  combination  centering  and  facing  tool  with  a  supporting 
bushing  c,  which  is  held  in  the  body  of  the  tool  by  two  head- 
less screws  d.  The  centering  tool  is  held  in  a  split  bushing  by 


0 

1 

1  — 
1 
1 

—  1 
1 

Fig.  23.   Centering  and  Facing  Tools 

set-screw  k.  The  turning  or  facing  tool  e  is  adjusted  to  cut  the 
required  diameter  by  set-screw  /  and  headless  screws  g,  the 
block  h  acting  as  a  fulcrum.  This  holder  is  used  when  the  work 
has  been  turned  before  centering,  and  it  is  also  found  con- 
venient for  centering  long  and  slender  work. 

Drills  and  Drilling.  —  For  general  work,  commercial  drills 
of  the  two-fluted  type  are  used  exclusively  on  the  Brown  & 


DRILL-HOLDERS 


Sharpe  automatic  screw  machines  for  drilling  cylindrical 
holes.  The  spiral  fluted  drill  is  used  for  drilling  machine  steel, 
Norway  iron,  etc.,  and  also  for  shallow  holes  in  brass;  but, 
when  deep  holes  are  to  be  drilled  in  brass,  a  straight-fluted 
drill  should  be  used  in  preference  to  a  spiral  drill,  as  it  breaks 
up  the  chips,  allowing  them  to  be  removed  with  greater  ease. 
The  shape  of  the  cutting  edge  of  the  drill  affects  the  shape  of 
the  chips  produced  and  also  the  amount  of  power  required 


[F 

=  4* 


-4 


3 


Fig.  24.   Various  Types  of  Drill-holders 

to  force  the  drill  into  the  work.  If  the  included  angle  of  the 
point  is  about  118  degrees,  and  if  the  point  is  ground  thin, 
it  will  produce  a  long,  curling  chip,  and  will  not  require  much 
power  for  drilling.  When  drilling,  if  the  edges  of  the  drill 
burn,  it  is  an  indication  that  the  surface  speed  is  too  high; 
if  the  drill  chips,  the  feed  is  too  great;  and  if  the  drill  splits 
at  the  point,  that  the  proper  clearance  has  not  been  given  at 
the  cutting  edges. 

For  shallow  holes,  the  best  results  are  obtained  by  giving 
a  rotary  motion  to  the  work  and  a  feeding  motion  to  the  drill, 
but,  when  drilling  deep  holes,  the  drill  and  the  work  should 
both  be  given  a  rotary  motion.  This  helps  to  clear  the  chips 
from  the  hole  and  also  allow  oil  to  penetrate  to  the  cutting 


Ii8  TOOL  EQUIPMENT 

point  of  the  drill.  When  drilling  deep  holes,  the  drill  should 
not  penetrate  into  the  work  more  than  i\  times  the  diameter 
of  the  drill  before  being  withdrawn.  For  drilling  deep  holes 
in  tool  and  machine  steel,  the  spiral-fluted  drill  is  generally 
used  with  good  results,  but,  for  drilling  deep  holes  in  brass, 
the  straight-fluted  drill  gives  better  satisfaction,  as  it  does  not 
produce  a  long,  curling  chip,  which  is  generally  objectionable. 

Drill-holders.  —  There  are  various  types  of  drill-holders 
used  in  the  automatic  screw  machine.  The  alignment  of  the 
turret  holes  with  the  spindle  is  usually  very  accurate  and  it 
is  not  necessary  to  have  a  floating  holder  for  holding  a  drill. 
At  A  in  Fig.  24  is  shown  a  common  form  of  drill-holder.  It  is 
flattened  on  the  sides  to  take  up  as  little  space  as  possible 
when  working  in  conjunction  with  the  cross-slide  tools.  A 
plain  bushing  as  shown  at  a  is  used.  At  B  is  shown  a  more 
expensive  holder  which  is  sometimes  used  for  holding  reamers 
and  counterbores  for  operating  on  a  piece  which  has  previ- 
ously been  drilled  concentric.  The  bushing  part  of  the  holder 
is  shown  at  b.  At  C  is  shown  a  holder  somewhat  similar  to 
that  shown  at  £,  but,  instead  of  the  shank  and  drill-holder 
being  in  one  piece,  a  separate  bushing  is  used.  For  ordinary 
work,  the  holder  shown  at  A  is  recommended. 

High-speed  Drill-holder.  —  A  high-speed  drill-holder  that 
can  be  used  on  the  larger  sizes  of  machines  for  increasing  the 
speed  of  small  drills  in  the  turret  is  shown  in  Fig.  25.  The  re- 
volving spindle  a  is  mounted  in  two  bronze  bearings  with  the 
driving  gear  b  shown  at  B.  The  thrust  is  taken  on  the  ball 
bearing  c  shown  at  C.  The  drill  chuck  d  is  of  the  spring  collet 
type.  The  shank  e  is  ground  to  fit  the  tool  hole  in  the  turret 
and  the  rear  end  of  this  shank  is  a  reservoir  for  oil  which  lu- 
bricates all  the  bearings  in  the  holder.  Sufficient  oil  should 
be  put  in  at  the  point  /  to  completely  fill  the  reservoir.  For 
holding  small  reamers,  the  spindle  a  is  especially  constructed 
to  receive  a  floating  type  of  reamer -holder  instead  of  the  drill- 
holder  shown.  This  holder  is  driven  by  a  shaft  running  through 
the  turret  shaft  and  a  small  pulley  belted  to  the  overhead 
works. 


COUNTERBORING  TOOLS 


119 


Counterboring  Tools.  —  Trouble  is  often  experienced  in 
using  counterbores  on  automatic  machines.  This  is  probably 
due  to  the  fact  that  counterbores  are  used  which  are  not 
adapted  for  the  work  on  which  they  operate.  Generally 
speaking,  there  are  several  reasons  for  the  unsuccessful  work- 
ing of  counterbores,  some  of  which  may  be  summed  up  as 
follows:  i.  Too  many  cutting  edges,  not  allowing  enough 
chip  space  and  also  not  providing  for  sufficient  lubrication. 


Fig.  25.   High-speed  Drill-holder 

2.  Too  much  cutting  surface  in  contact  with  the  work.  3. 
Insufficient  clearance  on  the  periphery  of  the  teeth.  4.  Im- 
proper location  of  the  cutting  edges  relative  to  the  center. 
5.  Improper  method  of  holding  the  counterbore.  6.  Improper 
grinding  of  the  cutting  edges.  7.  Too  weak  a  cross-section. 
8.  The  use  of  a  feed  and  speed  in  excess  of  what  the  tool  will 
stand. 

For  work  in  automatic  machines,  where  the  counterbore 
cannot  be  withdrawn  when  it  plugs  up  with  chips  and  seizes 
in  the  work,  the  tool  should  not  have  more  than  three  cutting 


I2O 


TOOL  EQUIPMENT 


teeth.  The  periphery  of  the  teeth  should  be  backed  off  eccen- 
trically, and  the  body  of  the  counterbore  should  taper  towards 
the  back.  The  amount  of  taper  generally  varies  from  0.020 
to  0.040  inch  per  foot.  The  relation  of  the  cutting  edge  to 
the  center  has  an  important  bearing  on  the  efficiency  of  the 


TAPER  FROM  ~  TO 
INCH  PER  FOOT 


32TOW\ 

OT    U 


B 

FROM  5°  TO  10° 


D 


FROM  10  TO  15 


BACKED  OFF  HELICALLY 


Fig.  26.   Three-fluted  Drill  —  Various  Types  of  Counterbores 

tool.  For  deep  counterboring,  where  the  difference  between 
the  diameter  of  the  teat  and  the  body  of  the  counterbore  is 
great,  the  cutting  edge  should  never  be  located  ahead  of  the 
center;  often,  if  it  is  located  a  little  behind  the  center,  better 
results  are  obtained;  but  this  rule  is  only  general,  as  the  ma- 
terial to  a  considerable  extent  governs  the  location  of  the 
cutting  edges.  It  is  advisable  to  have  the  cutting  edge  ahead 


COUNTERBORING  TOOLS  121 

of  the  center,  when  the  counterbore  is  to  be  used  as  a  facing 
tool  or  for  counterboring  brass,  provided  it  is  not  required  to 
enter  the  work  to  a  depth  greater  than  its  diameter. 

For  general  work,  the  cutting  edges  should  be  radial.  Straight 
flutes  are  suitable  for  either  brass  or  steel,  but  for  steel  it  is 
better  to  have  the  teeth  cut  spirally,  the  spiral  being  sufficient 
to  give  a  rake  of  from  10  to  15  degrees.  If  the  difference  be- 
tween the  diameter  of  the  pilot  and  the  body  of  the  counter- 
bore  is  not  very  great,  and  if  the  counterbore  must  extend 
into  the  work  to  a  depth  greater  than  its  diameter,  the  cutting 
edge  should  be  back  of  the  center,  that  is,  to  the  rear  of  the 
radial  line  parallel  to  the  cutting  face.  When  the  counter- 
bore  has  to  remove  considerable  material  or  enter  the  work 
to  a  depth  greater  than  its  diameter,  it  is  generally  advisable 
to  rough  out  the  hole  to  the  diameter  of  the  body  of  the  coun- 
terbore with  a  three-fluted  drill,  such  as  shown  at  A,  Fig.  26. 
Then  the  counterbore  is  used  only  for  squaring  up  the  shoulder 
at  the  bottom  of  the  hole.  This  method  is  especially  advisable 
when  counterboring  machine  or  tool  steel. 

At  B  is  shown  a  counterbore  which  can  sometimes  be  used 
to  advantage  on  brass  work,  but  which  is  not  recommended 
for  steel.  At  C  is  shown  another  counterbore  for  brass  work, 
which  has  three  cutting  edges,  and  at  D  is  shown  a  counter- 
bore  for  steel  work,  having  its  teeth  cut  spirally.  Teeth  cut 
on  a  spiral  which  will  produce  a  rake  angle  of  from  10  to  15 
degrees  are  generally  found  suitable  for  machine  or  tool  steel. 
Counterbores  of  the  type  shown  at  C  and  D  should  have  in- 
serted leaders  or  teats  to  facilitate  resharpening.  At  E  is 
shown  a  counterbore  which  is  recommended  for  work  having 
complicated  shapes,  or  requiring  to  have  two  or  more  di- 
ameters finished  with  the  same  tool.  This  tool  is  backed  off 
helically  as  shown,  thus  allowing  it  to  be  ground  and  still 
retain  its  initial  shape  and  size. 

The  counterbores  described  are  for  making  pieces  which 
permit  using  a  pilot  on  the  counterbore.  The  ordinary  method 
used  in  producing  holes  which  bottom  is  to  use  flat  drills  and 
combination  counterbores  and  facing  tools. 


122 


TOOL  EQUIPMENT 


Flat  Drills  and  Combination  Counterbores.  —  At  A  in  Fig. 
27  is  shown  a  flat  drill  which  is  used  for  roughing  out  a  hole 
having  one  diameter,  and  at  B  is  shown  the  counterbore  or 
facing  tool  which  is  used  for  squaring  it  up.  The  cutting  edge 
a  on  the  tool  should  be  set  about  one-tenth  times  the  diameter 


Machinery.N.Y. 


Fig.  27.   Flat  Drills  and  Combination  Counterbores 

ahead  of  the  center,  and  the  thickness  of  the  blade  b  should  be 
about  one-eighth  of  the  diameter.  At  C  is  shown  a  flat  drill 
or  counterbore  for  producing  a  hole  having  two  diameters, 
and  at  D  is  shown  the  combination  counterbore  and  facing 
tool  for  squaring  it  up.  This  counterbore  is  adjustable,  the 
part  a  being  adjusted  with  relation  to  part  b  by  means  of 
the  headless  screw  c}  thus  governing  the  distance  between  the 


COUNTERBORING  TOOLS 


123 


shoulders,  the  headless  screw  d  being  used  to  prevent  the 
part  a  from  rotating.  These  counterbores  can  be  used  for 
either  brass  or  steel  work,  but  for  steel  work  it  is  preferable 
to  use  a  spiral-fluted  drill  for  roughing  out  the  hole,  instead  of 
a  flat  drill,  as  the  material  can  be  removed  with  greater  ease 
and  rapidity. 

Holders    for     Counterbores.  —  For     counterbores    having 
leaders  or  pilots,  a  rigid  holder  should  not  be  used,  as  the 


Fig.  28.  Method  of  Holding  Counterbores  for  Various  Conditions 

leader  will  follow  the  hole  previously  drilled  or  reamed,  and  if 
the  counterbore  is  not  allowed  to  float,  it  will  produce  poor 
work,  and  a  broken  tool  will  sometimes  be  the  result.  At  A 
in  Fig.  28  is  shown  a  floating  holder  which  will  be  found  very 
serviceable.  The  sleeve  or  shank  a  is  made  to  fit  the  turret 
and  is  bored  out  from  ^V  to  yV  inch  larger  in  diameter  than  the 
shank  of  the  holder  b.  The  holder  b  is  kept  from  turning  by 
the  driving  pin  c,  which  is  made  a  driving  fit  in  the  part  b 
and  a  loose  fit  in  the  part  a.  The  hole  in  the  part  a  should 
be  about  sV  inch  in  diameter  larger  than  the  pin  c.  The  two 
headless  screws  d  are  used  for  adjusting  the  counterbore  so 
that  it  will  enter  easily  into  the  drilled  hole.  They  also  help 
to  keep  the  holder  b  from  turning.  It  is  good  practice,  when 


124 


TOOL  EQUIPMENT 


possible,  to  chamfer  the  hole  so  that  the  leader  will  enter  easily. 
The  counterbore  is  held  by  the  split  bushing  e  and  set-screw/. 
If  this  holder  is  properly  made  and  set  it  will  be  found  to  give 
good  results  for  general  work. 


Fig.  29.   Adjustable   Counterboring,   Boring  and  Recessing 
Toolholders 

At  B  is  shown  a  holder  for  holding  the  flat  counterbore 
shown.  The  holder  is  made  adjustable  so  that  the  tool  can  be 
set  concentric  with  the  center  of  the  work.  After  adjusting, 
the  part  a  is  held  tightly  against  the  part  b  by  the  cap-screws 
c.  The  counterbore  is  held  in  the  part  a  by  set-screw  d.  This 


REAMERS  125 

holder  is  also  found  very  serviceable  for  holding  a  counter- 
bore  when  the  hole  to  be  counterbored  penetrates  into  the  work 
to  a  distance  greater  than  its  diameter  and  a  chucking  drill 
has  been  used  to  rough  it  out. 

A  counterbore  holder  of  the  adjustable  type  is  shown  at  A 
in  Fig.  29.  The  front  holder  or  plate  a  is  bolted  firmly  to  the 
shank  b,  and  is  adjusted  by  means  of  four  set-screws  c,  only 
two  of  which  are  shown.  This  holder  is  made  adjustable  in 
order  to  set  the  cutting  tool  perfectly  concentric  with  the  hole 
in  the  work. 

Adjustable  Tool-holders  for  Boring  and  Recessing  Tools. 
-  The  tool-holder  shown  at  B,  Fig.  29,  is  used  for  a  boring 
tool.  The  front  part  of  this  tool-holder  is  adjustable  by  means 
of  two  set-screws  d,  which  work  through  the  shank  of  the 
clamping  bolt  e  and  in  this  way  secure  the  desired  adjustment 
to  set  the  boring  tool  concentric  or  to  the  correct  diameter. 

The  recessing  tool  shown  at  C  has  a  shank  /,  to  which  is  f  ul- 
crumed  a  holder  g  on  a  stud  h.  This  tool  is  operated  by  means 
of  a  cam  i  held  in  an  arm  j  that  is  clamped  to  the  cross-slide 
of  the  machine.  Cam  i  comes  in  contact  with  the  pin  k  on  the 
holder  and  operates  it  after  the  tool  has  advanced  into  the 
hole  in  the  work.  A  stud  in  the  sliding  part  of  this  holder  is 
spring-controlled  and  contacts  with  the  screw  k,  which  acts 
as  a  stop  for  setting  the  cutting  tool  in  a  concentric  position 
for  entering  the  hole  in  the  work. 

Reamers  for  Screw  Machine  Work.  —  When  reaming  holes 
in  automatic  screw  machines,  it  is  advisable  not  to  leave  any 
more  material  to  be  removed  by  the  reamer  than  is  absolutely 
necessary.  For  general  work,  the  following  allowances  will 
give  good  results  for  reamers  ranging  in  diameter  from  f  to 
f  inch.  For  reamers  over  f  inch  in  diameter,  a  drill  •$-%  inch 
less  in  diameter  is  generally  used;  this  would  leave  from  0.012 
to  0.015  inch  to  remove,  as  the  drill  will  cut  slightly  larger 
than  its  nominal  size. 

Diameter  of  reamer,  in  inches  i  •&  i  T\  f 

Diameter  of  hole  before  reaming      0.120      0.182       0.242       0.302       0.368 

Reamers  are  generally  made  slightly  tapering  towards  the 


126 


TOOL  EQUIPMENT 


back;  a  taper  varying  from  0.002  to  0.005  mc^  Per  foot  is 
generally  used,  and  a  less  taper  should  be  used  for  brass  than 
steel,  as  brass  work,  especially  thin  tubing,  contracts  and 
expands  more  readily  than  steel,  so  that,  if  a  perfect  hole  is 
desired,  the  reamer  should  be  tapered  but  slightly.  For  ream- 
ing machine  steel,  a  rose  reamer  is  generally  used,  as  it  has 
been  found  satisfactory  for  producing  straight  and  perfect 


ADJUST  TO  BRING 
REAMER  CONCENTRIC 
WITH  HOLE  IN  WORK 


Fig.  30.   Methods  of  Holding  Reamers 

holes.  This  reamer  tapers  towards  the  back  and  is  not  re- 
lieved on  the  periphery  of  the  cutting  edges,  the  end  of  the 
reamer  only  being  backed  off.  The  cutting  edges  of  reamers 
are  generally  cut  on  the  center  (radial)  for  steel,  but,  for  brass 
work,  they  are  sometimes  cut  slightly  ahead  of  the  center, 
which  produces  a  scraping  action,  and  makes  a  smooth  cut. 
For  brass,  the  cutting  edges  of  the  reamer  should  be  parallel 


REAMERS 


I27 


with  the  axis,  but  for  machine  steel  the  reamer  gives  better 
results  when  the  flutes  are  helical,  making  about  one  turn  in 
12  inches.  For  reaming  tapered  holes,  a  reamer  having  ser- 
rated flutes  gives  the  best  results,  and,  when  the  taper  is 
steep  (included  angle  greater  than  30  degrees),  the  finishing 
reamer  should  be  preceded  by  a  stepped  counterbore. 

Reamer  Holders.  —  The  method  of  holding  a  reamer  when 
applying  it  to  the  work  governs  to  a  considerable  extent  the 
quality  of  the  hole  produced.  When  reaming  a  deep  hole,  if 
the  reamer  is  held  rigidly,  it  will  nearly  always  produce  a 


Fig    31.   Swing  Tool  used  for  External  Cutting 

hole  which  will  be  tapered  and  large  in  diameter.  At  A  in 
Fig.  30  is  shown  a  floating  holder  which  is  sometimes  used. 
This  holder  is  cheaply  made,  but  is  not  recommended  for 
automatic  screw  machine  work,  although  it  can  sometimes 
be  used  to  advantage  on  the  hand  screw  machine.  One  of 
the  disadvantages  of  this  reamer  holder  is  that  the  reamer 
drops  down  as  shown  at  a,  if  much  clearance  is  allowed  be- 
tween the  diameter  of  the  reamer  shank  and  the  diameter 
of  the  hole,  thus  preventing  the  reamer  from  entering  easily 
into  the  work,  which  generally  results  in  a  broken  reamer. 

At  B  is  shown  a  more  efficient  holder,  especially  for  deep- 
hole  reaming.  The  reamer  is  guided  at  the  rear  by  a  cone- 
pointed  screw  b,  and  is  kept  from  rotating  and  is  guided  at 
the  same  time  by  the  two  cone-pointed  screws  c.  By  means 
of  these  screws,  the  reamer  can  be  set  so  that  it  will  enter  the 


128 


TOOL  EQUIPMENT 


drilled  hole  easily,  and  at  the  same  time  be  allowed  to  adjust 
itself  to  correspond  to  the  eccentricity  of  the  hole  in  the 
work.  The  small  hole  d  is  drilled  through  the  shank  of  the 
reamer,  allowing  the  cone-pointed  screws  to  enter.  This  holder 
will  be  found  very  satisfactory  for  holding  reamers  when  it  is 
not  necessary  to  remove  an  excessive  amount  of  material. 
At  C  is  shown  a  floating  holder  which  is  used  for  reaming 
shallow  holes.  The  reamer  is  held  rigidly  by  a  split  bushing 
and  set-screw  /.  The  reamer  is  set  concentric  with  the  hole 


\ 


Machinery, N.  Y. 


Fig.  32.  Raising  Block  used  for  Operating  Swing  Tools  on  Brown  & 
Sharpe  Machines 

in  the  work  by  loosening  the  cap-screws  g  and  then  locating 
it  in  the  hole  by  the  bevel  or  rounded  corners  on  the  end  of 
the  reamer. 

Swing  Tools  for  Turning.  —  Swing  tools  are  so  named  be- 
cause the  cutting  tool  is  held  in  a  swinging  holder  as  shown 
in  Fig.  31,  which  illustrates  one  of  the  designs  used  on  Brown  & 
Sharpe  automatic  screw  machines.  This  tool  is  held  in  the 
turret  of  the  machine  and  the  swinging  member  is  operated  by 
a  raising  block  equipped  with  either  an  adjustable  or  fixed 


SWING  TOOLS  129 

guide  plate,  which  comes  into  contact  with  the  screw  seen  at 
the  end  of  the  swinging  arm.  This  raising  block  (Fig.  32)  is 
held  under  the  toolpost  of  the  front  cross-slide  and  it  has  a 
guide  plate  E  that  can  be  set  at  an  angle  with  the  spindle  for 
generating  taper  surfaces.  The  exact  shape  of  this  plate  de- 
pends upon  the  nature  of  the  operation  and  the  shape  required 
on  the  work.  The  arm  D  which  carries  the  guide  plate  can 
be  adjusted  in  and  out  and  is  held  in  position  by  screws  d. 
The  screw  /  serves  to  adjust  guide  plate  E  which  is  locked  in 
position  by  screw  g. 

The   swing   tool  is  used   for   straight,    taper,    or   irregular 


Fig.  33.   Shaving  Tool  used  on  the  "Acme"  Multiple-spindle 
Automatic  Screw  Machine,  and  Examples  of  Work 

turning,  where  box-tools  or  circular  forming  tools  are  not 
applicable,  as  when  turning  long,  slender  work  of  irregular 
shape  or  when  turning  behind  shoulders.  The  work  is  often 
roughed  out  with  this  tool  and  finished  with  a  shaving  tool. 
The  swing  tool  is  also  used  for  cutting-off  finished  parts  when 
both  cross-slide  tools  are  used  for  forming  operations.  The 
shank  is  arranged  to  hold  a  back-rest  for  supporting  small 
flexible  work.  This  back-rest  or  support  is  inserted  in  the  hole 
in  the  shank  of  the  tool  and  the  V-shaped  supports  are  usually 
set  in  advance  of  the  tool. 

Recessing  Swing  Tools.  —  When  it  is  necessary  to  chamfer 
inside  of  a  hole,  or  to  enlarge  the  central  part  of  a  hole  so  that 


130 


TOOL  EQUIPMENT 


a  bearing  surface  will  be  left  at  the  ends  only,  this  may  be 
done  on  the  automatic  screw  machine  by  the  use  of  a  swing 
tool.  The  design  used  on  the  Brown  &  Sharpe  machine  for 
internal  chamfering  and  recessing  is  similar  in  principle  to 
the  one  shown  in  Fig.  3 1 ,  which  is  intended  for  .external  work, 
except  that  the  swinging  arm  is  arranged  for  holding  the 
shank  of  boring  or  recessing  tools.  The  guide  plate  which 
controls  the  movement  of  the  swinging  arm  is  shaped  to  suit 
the  work.  A  recessing  or  chamfering  operation  should  always 
precede  a  reaming  operation,  so  that  all  burrs  formed  by  the 
recessing  tool  will  be  removed  by  the  reamer. 


OOL  IS  ASSEMBLED  FOR  SECOND  POSITION 
TO  ASSEMBLE  FOR  THIRD  POSITION 
TURN  BASE  UPSIDE  DOWN 


Machinery 


Fig.  34.   Shaving  Tool-holder  with  Roller  Support 

Shaving  Tools  for  Screw  Machines.  —  When  forming  work 
of  irregular  shape  or  contour,  in  the  automatic  screw  ma- 
chine, it  is  common  practice  to  use  a  shaving  tool  which  oper- 
ates tangentially  to  the  work  and  takes  a  light  finishing  cut. 
Shaving  tools  are  used  to  follow  circular  forming  tools  for 
producing  a  smooth,  accurately  finished  surface,  and  they  are 
also  used  to  completely  form  the  work  without  any  previous 
roughing  operation.  The  amount  removed  by  the  shaving 
tool  varies  somewhat  with  the  size  of  the  work.  When  taking 
shaving  cuts  on  small  parts,  from  0.003  to  0.005  inch  might 
be  removed,  while  for  larger  parts  the  allowance  is  often 
greater.  A  design  of  shaving  tool  which  is  used  on  the  Acme 


SHAVING  TOOLS  131 

multiple-spindle  automatic  is  shown  in  Fig.  33.  This  tool  is 
used  in  the  second  or  third  side  positions  and  removes  0.002 
or  0.003  inch  of  stock  left  by  the  forming  tool.  The  blades 
H  and  G  of  this  tool  are  made  in  pairs.  One  blade  is  used  as 
a  rest  and  does  no  cutting,  whereas  the  other  one  has  a  cutting 
edge.  The  holder  H  is  adjusted  by  means  of  a  screw  for  lo- 
cating the  two  parts  H  and  G  the  required  distance  apart. 
The  supporting  blade  is  slightly  longer  than  the  shaving  tool, 
so  that  it  comes  into  contact  with  the  work  slightly  in  advance 
of  the  tool.  The  support  and  the  shaving  blade  are  not  exactly 
parallel,  the  blade  being  inclined  one-half  degree  to  provide  a 
slight  clearance. 

Another  design  of  Acme  shaving  tool  which  has  proved 
very  effective  on  wide  and  difficult  cuts  is  shown  in  Fig.  34. 
This  tool  is  similar  in  its  general  construction  to  the  design 
shown  in  Fig.  33,  except  that  it  is  equipped  with  a  roller  type 
of  support.  The  cutting  edge  of  the  shaving  tool  should  be 
exactly  in  line  with  the  axis  of  the  supporting  roller.  The 
shaving  blades  and  supports  are  made  from  Jessop's  tool  steel. 
For  cutting  brass,  Jessop's  high-speed  steel  has  been  found  to 
give  better  results.  When  the  support  and  shaving  tool  have 
an  irregular  form,  the  surfaces  should  be  smoothly  finished 
before  the  tool  is  hardened  and  then  all  the  surfaces  are  lapped 
by  the  work  running  between  them. 

The  tools  illustrated  in  Figs.  33  and  34  are  only  recommended 
for  taking  light  finishing  cuts.  The  allowance  for  shaving 
depends  to  some  extent  upon  the  nature  of  the  work  and  the 
kind  of  tools  used  prior  to  the  shaving  operation.  The  allow- 
ances for  various  diameters  of  stock  should  be  about  as 
follows : 

Amount  to  Remove 
Diameter  in  Inches  in  Inches 

iV  to    i  0.0015 

^  to     \    O.OOlS 

£  to      |    0.0020 

f  to    f  0.0023 

|  tO    1 1    0.0026 

1^  to    Ij    O.OO28 

i  j  to  1 1 0.0030 

l|  tO    2\    0.0032 


132 


TOOL  EQUIPMENT 


Fig.  35  shows  a  type  of  shaving  tool  and  tool-holder  which 
does  not  have  a  support  for  the  work.  This  type  of  tool  is 
employed  when  the  work  is  so  rigid  that  a  support  is  unneces- 
sary. When  a  shaving  tool  is  not  preceded  by  a  forming  tool, 
and  if  the  work  is  long  in  proportion  to  its  diameter,  it  is 
advisable  to  grind  the  end  of  the  shaving  tools  so  that  a  shear- 
ing cut  will  be  taken  in  each  way  from  the  heaviest  part  of  the 
cut,  in  order  to  remove  the  material  more  easily.  In  other 
words,  the  end  of  the  tool  is  beveled  each  way  from  the  part 
that  will  take  the  heaviest  cut,  so  that  a  point  is  formed  which 
first  comes  into  contact  with  the  work.  The  angles  for  the 
cutting  point  of  the  tool,  as  indicated  by  the  detailed  views 
to  the  right  in  Fig.  35,  should  be  about  as  follows:  For  brass 


Machinery 


Fig.  35.    Shaving  Tool  and  Holder  for  Long  Work 

rods,  A  equals  20  degrees;  for  machine  steel,  30  degrees;  for 
tool  steel,  40  degrees.  For  brass  rods,  B  equals  30  degrees; 
for  machine  steel,  40  degrees;  for  tool  steel,  50  degrees.  For 
brass  rods,  C  equals  10  degrees;  for  machine  steel,  15  degrees; 
for  tool  steel,  15  degrees.  Of  course,  these  angles  may  vary 
more  or  less  without  appreciably  affecting  the  action  of  the 
tool. 

Dies  for  Screw  Machine  Work.  —  The  common  form  of 
spring  screw  threading  die  equipped  with  a  clamping  ring 
for  making  slight  diameter  adjustments  has  been  used  exten- 
sively on  automatic  screw  machines.  For  ordinary  use,  the 
adjustable  spring  dies  are  often  recommended,  because  they 
can  readily  be  ground  and  adjusted  for  size  and  are  considered 
economical.  There  are  two  methods  of  making  the  spring 
screw  threading  dies.  One  is  to  use  a  hob  tap  which  is  from 


DIES   FOR   SCREW  MACHINES  133 

0.005  to  0.015  inch  larger  than  the  standard  size  of  the  thread 
in  order  to  provide  clearance,  and  then  close  in  the  ends  of  the 
dies  by  the  adjusting  ring  or  clamp.  A  preferable  method  is 
to  tap  out  the  die  from  the  rear  with  a  taper  hob  tap,  leaving 
the  front  end  of  the  die  about  0.002  inch  oversize.  The  hob 
tap  should  have  a  taper  varying  from  T\  to  J  inch  per  foot. 
The  round  split  dies  or  "  button  dies,"  as  they  are  commonly 
called,  are  also  extensively  used.  While  a  round  or  button  die 
cannot  be  resharpened  readily  like  a  spring  die,  its  initial  cost 
is  considerably  less,  so  that  it  can  be  discarded  when  dull. 
The  button  dies,  owing  to  their  shape,  are  not  distorted  as  much 
as  the  spring  screw  dies  when  hardening,  and  they  can  be  held 
more  rigidly  in  the  holder.  The  cutting  edges  on  spring  screw 
dies  should  be  radial  for  brass  and  about  one-tenth  the  di- 
ameter ahead  of  the  center  for  Norway  iron,  machine  steel, 
etc.  The  cutting  edges  of  button  dies  can  be  ahead  of  the 
center  about  one-tenth  of  the  diameter. 

Holders  for  Threading  Dies.  —  There  are  many  different 
designs  of  die-holders  for  use  on  automatic  screw  machines. 
Many  of  these  die-holders  are  applicable  to  different  makes 
of  machines,  while  others  are  designed  more  especially  for  a 
given  type.  The  Brown  &  Sharpe  Mfg.  Co.  makes  two  general 
styles  of  die-  and  tap-holders,  which  are  known  as  the  non- 
releasing  type  and  the  releasing  type.  The  non-releasing  type 
is  so  arranged  that  the  die  is  free  to  move  axially  a  limited 
distance.  The  releasing  type  is  so  designed  that,  when  the 
turret  stops  feeding  forward,  a  slight  additional  forward  move- 
ment on  the  part  of  the  die  causes  the  driving  members  of  the 
die-holder  to  disengage  so  that  the  die  spins  around  with  the 
work  until  the  spindle  reverses;  the  die  then  starts  to  rotate 
backwards  with  the  spindle  and  work,  but  this  backward 
motion  is  automatically  stopped  by  the  die-holder,  so  that, 
as  the  die  is  held  stationary,  it  is  unscrewed  as  the  spindle 
continues  to  revolve. 

The  non-releasing  type  of  tap-  and  die-holder  is  used  on 
a  very  large  percentage  of  the  work  done  on  Brown  &  Sharpe 
automatic  screw  machines;  in  fact,  the  releasing  type  is  gen- 


134 


TOOL  EQUIPMENT 


erally  used  in  order  to  eliminate  the  use  of  a  threading  lobe 
that  is  too  pointed.  For  instance,  some  lobes  which  are  de- 
veloped for  the  non-releasing  type  of  holder  have  a  thin  sharp 
point,  but  by  using  the  releasing  type  a  certain  amount  of 
dwell  can  be  allowed  at  the  top  of  the  lobe  which  is  some- 
times desirable  simply  for  strengthening  the  lobe.  The  non- 
releasing  type  will  enable  threads  to  be  cut  to  as  uniform  a 
distance  from  the  shoulder  as  the  releasing  type. 

Releasing  Die-holder.  —  A  releasing  type  of  die-holder 
for  button  dies  is  shown  in  Fig.  36.  When  the  die-holder 
or  spindle  a  draws  out  from  the  body  6,  the  driving  pins  c 


Fig.  36.  Releasing  Die-holder 

are  also  withdrawn,  so  that  the  ends  of  these  pins  are  flush 
or  even  with  the  plate  m.  When  the  machine  spindle  is  re- 
versed, the  spindle  a  revolves  with  the  work  and  the  ball  e 
is  thrown  out  of  the  deep  part  of  the  pocket  in  which  it  nor- 
mally rests,  as  shown  at  B,  into  the  position  shown  at  C. 
This  outward  movement  of  the  ball  locks  the  die-holder,  thus 
allowing  the  die  to  be  backed  off  of  the  work  as  the  spindle 
continues  to  revolve  in  a  reverse  direction.  When  the  ball  e 
is  placed  in  the  pocket  /,  the  die-holder  may  be  used  for  cut- 


DIES  FOR  SCREW  MACHINES 


135 


ting  a  right-hand  thread,  whereas,  when  the  ball  is  in  pocket 
g,  the  die-holder  may  be  used  for  left-hand  threads. 

Another  design  of  releasing  die-holder,  which  is  a  product 
of  the  Cleveland  Automatic  Machine  Co.,  is  shown  in  Fig.  37. 
This  is  known  as  the  "  Silent"  die-holder  because  it  is  so  de- 
signed that  the  driving  members  do  not  strike  against  each 
other  after  disengagement  at  the  forward  end  of  the  turret 
travel.  The  holder  has  a  sleeve  which  is  gripped  in  the  turret 
and  a  stem  which  fits  inside  of  this  sleeve.  In  the  driving 
mechanism,  there  are  two  pieces  A,  of  the  same  shape,  which 
are  held  in  position  by  screws  B.  The  driving  pins  E,  which 


Machinery 


Fig.  37.   Sectional  View  of  Cleveland  Releasing  Die-holder 

come  in  contact  with  parts  A  when  threading,  are  plain  pins 
having  heads  which  are  somewhat  larger  than  the  body  and 
flattened  on  the  sides.  Parts  A  and  E  are  held  in  their  cor- 
rect positions  by  a  weak,  piano-wire  coiled  spring  7,  which  is 
just  strong  enough  to  keep  the  two  large  members  of  the  die- 
holder  together.  After  the  turret  has  advanced  to  the  end  of 
its  travel,  and  the  driving  points  A  and  E  are  disengaged,  the 
small  springs  G  swing  parts  A ,  which  are  pivoted  on  screws  B, 
back  so  that  their  angular  ends  are  nearly  in  a  straight  posi- 
tion, or  in  a  plane  at  right  angles  to  the  axis  of  the  holder. 
By  this  movement,  the  ends  of  driving  pins  E  and  parts  A 
clear  one  another,  regardless  of  how  long  the  turret  remains 
in  the  advanced  position,  thereby  eliminating  any  pounding 
and  damaging  of  the  parts  which  carry  the  die  or  tap  forward. 
The  pieces  C  have  no  duty  to  perform  when  the  die-holder  is 
on  the  threading  operation,  but,  when  the  spindle  reverses, 


TOOL  EQUIPMENT 


parts  C  drop  into  the  slots  H  and  hold  the  die-holder  rigid 
while  the  turret  recedes.  These  pieces  are  constantly  held  in 
their  position,  whether  in  the  slots  or  otherwise,  by  springs  K. 
The  slots  H,  into  which  pieces  C  fit,  are  milled  on  a  fairly 
large  diameter,  and  this  part  of  the  mechanism  is  designed  to 
last  indefinitely. 

When  changing  the  die-holder  for  cutting  left-hand  threads, 
the  screws  B  are  removed  and  the  parts  A  are  turned  over  so 
that  the  straight  driving  side  is  in  the  opposite  direction  in 
both  cases.  The  screws  /  and  F  are  also  removed  so  that 


Machinery 


Fig.  38.   Telescopic  or  Combination  Die-  and  Tap-holder 

pieces  C  can  be  turned  around  to  reverse  the  position  of  the 
driving  sides.  The  small  screws  F  fit  into  slots  E  and  simply 
hold  the  pieces  C  in  their  proper  position. 

Telescopic  Die-  and  Tap-holder.  —  A  telescopic  or  combi- 
nation die-  and  tap-holder,  designed  for  use  on  the  "Acme 
automatics,"  is  shown  in  Fig.  38.  With  this  die-holder,  two 
threading  operations  may  be  completed  at  the  same  time;  that 
is,  two  dies  of  different  diameters  can  be  used,  or  a  die  and  tap 
as  required,  the  tap  being  held  in  the  rear  part  of  the  holder. 
This  special  tool  consists  of  a  shank  A  in  which  a  button  die  B 
is  held  by  the  cone-pointed  screw  shown.  When  a  tap  is  to 
be  used,  the  button  die  is  replaced  by  a  bushing  for  holding 


DIES  FOR  SCREW  MACHINES 

the  tap.  The  front  part  C  of  the  holder,  which  carries  the  lead- 
ing button  die,  is  a  sliding  fit  on  a  key  in  member  A.  To  en- 
able the  cutting  of  two  threads  of  different  pitch,  the  front 
member  C  is  restrained  by  two  coil  springs  D,  which  allow  it 
to  lead  out  in  advance  of  the  other  part  of  the  die-holder,  and 
as  the  shank  A  is  held  in  the  die  spindle,  which  also  is  spring- 
controlled  as  regards  the  leading  out  of  the  spindle,  it  is  evi- 
dent that  the  lead  of  the  two  members  is  controlled  by  the 
pitch  of  the  thread  in  the  dies.  A  stop-screw  E  is  provided  for 
locating  the  holder  C  in  its  backward  position,  so  that  the  two 


Fig.  39.   Self -opening  Die  Attachment  on  Acme  Machines 

dies  will  always  be  in  the  same  relation  to  each  other  when 
starting  to  cut.  Clearance  cuts  are  provided  in  both  members 
to  facilitate  the  removal  of  chips. 

Self-opening  Die  Operating  Attachment.  —  Fig.  39  shows  a 
self-opening  die  applied  to  an  Acme  multiple-spindle  auto- 
matic. This  type  of  die  is  recommended  for  cutting  long  threads 
of  accurate  pitch.  The  working  mechanism  of  the  die-holder 
is  enclosed  within  the  body  which  carries  the  cam-operating 
blocks.  The  chasers  have  closing  and  adjusting  cams  milled 
on  their  outer  ends  that  bear  against  the  cam-operating  blocks. 
The  adjustment  of  the  chasers  is  controlled  by  a  fine-pitch 
screw,  the  amount  of  adjustment  being  indicated  by  microme- 


138  TOOL  EQUIPMENT 

ter  graduations.  This  die  is  operated  by  an  arm  /  which  en- 
gages a  groove  in  the  outer  body  of  the  die-holder  and  shifts  it 
axially  relative  to  the  inner  member  which  holds  the  chasers, 
thus  causing  the  latter  to  move  inward  or  outward,  accord- 
ing to  the  direction  of  movement.  Fig.  39  shows  the  attach- 
ment in  the  position  it  occupies  when  the  die  is  to  be  opened 
after  cutting  the  thread.  The  die  is  rotated  by  the  threading 
spindle  in  the  usual  manner.  A  shoe  7,  similar  in  shape  to 
shoe  7,  is  connected  to  the  rear  end  of  the  threading  spindle, 
and  is  held  on  a  spindle  K  which  is  retained  in  the  bracket  L 
attached  to  the  end-working  tool-slide. 

In  operation,  as  the  end- working  tool-slide  advances  the 
chasers  in  the  die  come  in  contact  with  the  work  and  start  to 
cut  the  thread.  When  the  pitch  of  the  thread  is  greater  than 
the  forward  advance  of  the  tool-slide,  the  spring  M  is  com- 
pressed as  the  threading  spindle  is  withdrawn;  this  action 
carries  forward  the  two  arms  7  and  /  at  the  same  speed.  When 
the  die  chasers  have  advanced  on  the  work  to  the  required 
distance,  the  sleeve  N  comes  into  contact  with  adjustable 
stop  0  held  in  bracket  P.  This  bracket  is  provided  with  an 
adjusting  screw  and  is  attached  to  the  casing  enclosing  the 
cylinder.  As  the  die  continues  to  cut,  the  outer  body  A  of 
the  die-holder  is  held  back  by  arm  7  and  the  chasers  advance 
until  they  come  out  of  contact  with  the  cam-operating  blocks, 
allowing  the  head  to  spring  open;  then,  as  the  end- working 
tool-slide  moves  back,  the  lever  Q  strikes  the  rear  dog  R  and 
pulls  the  chaser  head  back  into  the  casing  and  closes  the  die, 
ready  for  cutting  the  next  thread. 

Taps  for  Automatic  Screw  Machines.  —  When  tapping 
holes  in  the  automatic  screw  machine,  there  is  tendency  for 
the  chips  to  clog  back  of  the  cutting  edges,  thus  subjecting  the 
tap  to  excessive  torsional  strains  at  the  moment  its  movement 
is  reversed  relative  to  the  work  for  backing  it  out  of  the  hole. 
In  order  to  prevent  the  breaking  of  taps,  the  flutes  should  be 
relatively  large  in  order  to  provide  ample  space  for  the  chips, 
the  lands  being  made  just  strong  enough  to  resist  the  cutting 
pressure.  The  flutes  may  be  milled  with  an  85-degree  double- 


TAPS  FOR   SCREW  MACHINES  139 

angle  cutter  having  an  inclination  of  55  degrees  on  one  side 
and  30  degrees  on  the  other.  Screw  machine  taps  in  all  sizes 
smaller  than  i£  inch  in  diameter  should  have  four  flutes,  and 
for  larger  diameters,  six  flutes.  The  width  of  the  lands  for 
different  diameters  should  be  about  as  follows:  Diameter, 
J  inch,  land  width,  y^  inch;  diameter,  f  inch,  land  width, 
-/2  inch;  diameter,  \  inch,  land  width,  f  inch;  diameter,  J 
inch,  land  width,  A  inch;  diameter,  i  inch,  land  width,  J 
inch.  Ordinarily  the  thread  is  relieved  only  on  the  top  of  the 
chamfered  end.  If  the  straight  part  or  body  of  the  tap  is 
relieved,  the  chips  are  liable  to  wedge  in  between  the  tops  of 
the  threads  on  the  lands  of  the  tap  and  the  thread  in  the  hole, 


,GRIND  GROOVE  AFTER  HARDENING 


Fig.  40.   A  Tap  Suitable  for  Norway  Iron  and  Machine  Steel 

which  might  result  in  either  breaking  the  tap,  owing  to  the 
excessive  torsional  strain,  or  in  damaging  the  thread  in  the 
hole.  The  chamfered  end  of  screw  machine  taps  is  usually 
very  short,  because  the  tap,  in  most  cases,  is  required  to  cut 
threads  close  to  the  bottom  of  a  hole. 

The  amount  of  chamfer  required  on  taps  for  various  pitches 
is  as  follows: 

From  14  to  24  threads 2\  threads. 

From  26  to  32  threads 3     threads. 

From  36  to  48  threads 4    threads. 

From  56  to  80  threads 5     threads. 

In  regard  to  the  diameter  of  the  shank,  manufacturers  making 
a  specialty  of  these  taps  recommend  that  the  shank  diameter 
be  made  to  correspond  with  the  outside  diameter  of  a  spring 
screw  die  for  cutting  the  same  size  of  thread  as  the  tap  is 
intended  for,  so  that  the  same  holder  may  be  used  for  both 
the  tap  and  the  die.  If  a  tap  is  to  be  used  for  cutting  triple 


140  TOOL  EQUIPMENT 

or  quadruple  threads,  the  flutes  should  be  helical  so  that  they 
will  be  at  right  angles  to  the  teeth  and  form  square  cutting 
edges. 

While  an  ordinary  machine  tap  may  be  used  for  tapping 
brass  in  the  screw  machine,  it  does  not  give  satisfactory  results 
when  tapping  such  material  as  Norway  iron,  machine  steel, 
etc.  The  tap  shown  in  Fig.  40  has  proved  satisfactory  for 
materials  of  the  kind  mentioned.  The  end  of  this  tap  is  ground 
at  an  angle  of  about  55  degrees  and  is  slightly  cupped  out  at 
the  center  and  backed  off  as  indicated  in  the  end  view.  The 
tap  should  be  slightly  tapered  towards  the  back  for  clearance. 
A  groove  is  ground  the  entire  length  of  the  threaded  part 
after  the  tap  has  been  hardened.  This  groove  allows  the  oil 
to  reach  the  point  of  the  tap  and  also  provides  clearance  for 
the  chips.  When  made  from  Stubb's  imported  drill  rod  and 
carefully  hardened,  this  tap  can  be  worked  at  a  cutting  speed 
of  from  35  to  40  feet  per  minute. 

Some  taps  intended  especially  for  threading  copper  have  an 
odd  number  of  flutes  which  are  cut  spirally.  The  Echols 
patent  tap,  made  by  the  Pratt  &  Whitney  Co.,  has  proved 
effective  for  cutting  clean  threads  in  copper  and  tough  ma- 
terials, such  as  gun-metal,  etc.  This  style  of  tap  has  an  odd 
number  of  flutes  and  each  alternate  tooth  is  omitted,  the 
arrangement  being  such  that  each  tooth  is  followed  by  a  blank 
space  on  the  following  land,  which,  in  turn,  is  followed  by  a 
tooth  on  the  next  successive  land. 

Knurling  Tools.  —  The  tools  used  for  knurling  the  edges 
of  screw-heads,  etc.,  in  automatic  screw  machines,  are  held 
either  on  the  cross-slide  or  in  the  turret,  their  position  de- 
pending upon  the  location  of  the  surface  to  be  knurled  or  the 
arrangement  of  the  other  tool  equipment.  There  are  three 
general  methods  of  presenting  knurls  to  the  work.  When  the 
knurling  tool  is  attached  to  the  cross-slide,  it  may  be  forced 
against  the  work  either  radially  or  tangentially  and,  when  the 
knurling  tool  is  held  in  the  turret,  two  knurls  move  along  the 
surface  of  the  work  on  opposite  sides  and  parallel  with  its 
axis. 


KNURLING  TOOLS 


141 


A  cross-slide  type  of  knurl-holder  is  shown  in  Fig.  41.  The 
knurl  operates  on  the  top  side  of  the  work  as  the  cross-slide 
moves  laterally;  as  this  movement  is  continued,  the  circular 
cutting-off  tool  back  of  the  knurl  severs  the  finished  part, 
and  then  the  cross-slide  and  knurl  return  to  the  starting  posi- 
tion. The  knurl-holder  is  held  to  the  outer  face  A  of  the  rear 
cross-slide  tool-holder,  by  means  of  screw  B,  which  also  holds 
the  circular  cutting-off  tool.  The  distance  C  from  the  knurl 
to  the  cutting-off  tool  may  be  changed  in  accordance  with 


Fig.  41.   Rear  Cross-slide  Knurl-holder 

the  location  of  the  knurled  surface  relative  to  the  end  of  the 
work.  This  design  of  knurl-holder  can  only  be  used  on  a  tool- 
holder  which  carries  the  cutting-off  tool,  because  the  finished 
piece  must  be  severed  from  the  bar  before  the  knurl  can  return 
to  the  starting  position. 

Universal  Cross-slide  Knurling  Tool.  —  Another  design  of 
cross-slide  knurling  tool  is  shown  in  Fig.  42.  This  design  is 
more  complicated  and  expensive  than  the  one  previously 
described,  but  it  can  be  appli-ed  to  a  wider  range  of  work  and 
may  be  used  in  conjunction  with  either  circular  forming  or 
cutting-off  tools  on  the  front  cross-slide.  The  knurl  is  held 
in  arm  F,  which  is  pivoted  to  lever  C,  and  this  lever  is  mounted 
on  a  pin  upon  which  it  has  a  certain  amount  of  adjustment 
for  locating  the  knurl  relative  to  the  work  in  a  lengthwise 


142 


TOOL  EQUIPMENT 


direction.  The  nuts  M  on  the  stud  shown  serve  to  hold  arm 
C  and  also  provide  adjustment  for  raising  or  lowering  arm  F 
in  accordance  with  the  diameter  of  the  part  to  be  knurled. 
As  the  knurl  passes  over  the  stock  on  the  outward  movement 
of  the  cross-slide,  the  nuts  H  bear  against  the  face  B  of  the 


L     K 


Fig.  42.  Universal  Cross-slide  Knurl-holder 

lug  shown,  and  spring  K  is  compressed;  when  the  knurl  has 
cleared  the  work  and  the  pressure  on  the  spring  is  released, 
nut  J  is  forced  against  the  opposite  side  of  the  lug  and  arm  F 
swings  outward,  so  that  the  knurl  clears  the  work  on  the 
return  movement. 

Turret  Knurling  Tools.  —  Knurling  tools  which  are  held 
in  the  turret  and  move  parallel  with  the  work  usually  have 


KNURLING  TOOLS  143 

two  knurls  which  engage  the  work  on  opposite  sides.  The 
design  that  is  used  on  the  Brown  &  Sharpe  machines  is  shown 
in  Fig.  43.  The  knurls  have  teeth  which  are  parallel  to  the 
axis  so  that  they  may  by  used  for  either  straight  or  cross- 
knurling.  Each  knurl-holder  A  may  be  set  to  the  different 
angular  position  required,  by  means  of  the  graduations  on  the 
lugs  B  in  which  the  knurl-holders  are  inserted.  These  lugs  are 
clamped  by  nuts  C  and  are  adjustable  in  the  main  holder  F 
for  varying'  the  distance  between  the  knurls,  in  accordance 


Fig.  43.  Brown  &  Sharpe  Adjustable  Turret  Knurl-holder 

with  the  diameter  of  the  surface  to  be  knurled.  This  adjust- 
ment is  effected  by  screws  D  which  are  locked  by  screws  E. 

Opening  and  Closing  Type  of  Knurl-holder.  —  It  is  some- 
times necessary  to  use  a  turret  tool  for  knurling  a  diameter 
which  is  either  of  the  same  size  or  smaller  than  a  preceding 
part  of  the  work.  For  knurling  operations  of  this  kind,  a 
special  knurl-holder  is  required  which  is  so  designed  that  the 
knurls  will  move  inward  to  the  working  position  at  a  prede- 
termined point  and  then  open  automatically  after  the  required 
length  has  been  knurled. 

Double  Knurl-holder  for  Cross-slides.  —  The  double  ad- 
justable knurl-holder  shown  in  Fig.  44  was  designed  primarily 
for  use  on  the  Acme  multiple-spindle  machines.  It  is  usually 


144 


TOOL  EQUIPMENT 


held  on  a  top  working  tool-slide.  The  shank  A  is  slotted  at 
the  end  to  receive  a  swinging  member  B  which  is  pivoted  on 
screw  C.  The  lower  knurl  is  retained  in  holder  B  and  the  upper 
knurl  in  an  adjustable  holder  D,  which  is  held  in  position  by 
cap-screw  E  which  is  backed  up  by  screw  F.  The  movement 
of  part  B  is  controlled  by  the  stop-screw  G  against  which  the 
holder  is  held  by  a  bevel  pin  H  and  coil  spring  /.  This  con- 
struction gives  a  certain  amount  of  flexibility,  thus  making 
it  unnecessary  to  set  the  holder  accurately  relative  to  the 
work,  as  it  is  self-adjusting. 

The  Teeth  of  Knurls.  —  The  teeth  of  knurls  may  be  either 


Machinery 


Fig.  44.   Double  Knurl-holder  of  the  Adjustable  Type  for  Use  on  Top- 
or  Side-working  Tool-slides 

straight  or  parallel  with  the  axis,  or  they  may  be  at  an  angle 
with  the  axis.  Knurls  having  straight  teeth  are  presented 
to  the  work  so  that  these  teeth  are  parallel  with  the  axis  of 
the  work  when  straight  knurling,  similar  to  the  milled  edge  of 
a  coin,  is  desired.  By  applying  two  knurls  of  this  type  to 
opposite  sides  of  the  work  and  inclining  them  to  the  axis  of 
the  work,  a  cross  or  diamond  knurling  is  obtained.  A  similar 
form  of  knurling  may  also  be  obtained  by  using  a  pair  of 
knurls  which  have  right-  and  left-hand  helical  teeth  and  mount- 
ing the  knurls  in  their  holders  so  that  their  axes  are  parallel 
with  the  axis  of  the  work.  Knurls  also  differ  in  regard  to  their 
form,  some  being  cylindrical  for  operating  upon  plain  cylin- 


KNURLING  TOOLS  145 

drical  surfaces,  whereas  others  are  made  concave  to  conform 
to  the  convex  head  of  a  screw  or  other  part  that  requires 
knurling. 

Straight  Knurls.  —  Straight  knurls  or  those  having  teeth 
which  are  parallel  with  the  axis  are  generally  cut  in  the  milling 
machine  by  the  use  of  a  cutter  of  the  desired  angle.  It  is  im- 
portant to  select  a  suitable  angle  for  the  teeth  for  knurling 
different  materials.  A  " blunt  knurl"  will  work  better  on  soft 
materials  than  one  with  teeth  of  a  more  acute  angle.  The 
following  included  angles  for  the  teeth  have  been  found  satis- 
factory for  the  materials  specified: 

Brass  and  hard  copper    90  degrees. 

Gun  screw  iron 80  degrees. 

Norway  iron  and  machine  steel 70  degrees. 

Drill  rod  and  tool  steel 60  degrees. 

When  laying  out  a  set  of  cams  for  knurling  operations,  it 
is  necessary  to  know  the  depth  of  the  tooth  in  the  knurl. 
If  d  =  depth  of  tooth  in  knurl;  p  =  circular  pitch  of  knurl; 
a  —  included  tooth  angle  of  knurl;  then,  for  all  practical  pur- 
poses, the  depth  may  be  calculated  as  follows:  When, 

a  =  gp  degrees,  d  =  -, 

a  =  80  degrees,  d  =  -  x  tan  50  degrees, 
2 

a  =  70  degrees,  d  =  -  x  tan  55  degrees, 
2 

a  =  60  degrees,  d  =  -  x  tan  60  degrees. 
2 

Concave  Knurls.  —  The  radius  of  a  concave  knurl  should 
not  be  the  same  as  the  radius  of  the  piece  to  be  knurled. 
If  the  knurl  and  the  work  are  the  same  radius,  the  material 
compressed  by  the  knurl  will  be  forced  down  on  the  shoulder  D 
and  spoil  the  appearance,  of  the  work.  A  design  of  concave 
knurl  is  shown  in  Fig.  45,  and  all  the  important  dimensions 
are  designated  by  letters.  To  find  these  dimensions,  the  pitch 
of  the  knurl  required  must  be  known,  and  also,  approximately, 


146 


TOOL   EQUIPMENT 


the  throat  diameter  B.  This  diameter  must  suit  the  knurl- 
holder  used,  and  be  such  that  the  circumference  contains 
an  even  number  of  teeth  with  the  required  pitch.  When  these 
dimensions  have  been  decided  upon,  all  the  other  unknown 
factors  can  be  found  by  the  following  formula :  Let  R  =  radius 
of  piece  to  be  knurled;  r  =  radius  of  concave  part  of  knurl; 
C  =  radius  of  cutter  or  hob  for  cutting  the  teeth  in  the  knurl; 
B  =  diameter  over  concave  part  of  knurl  (throat  diameter); 
A  =  outside  diameter  of  knurl;  d  =  depth  of  tooth  in  knurl; 
P  =  pitch  of  knurl  (number  of  teeth  per  inch  circumference) ; 

p  =  circular    pitch    of    knurl; 
then,   r  =  R  +  \&\    C  =  r •+  d', 
A  =  B  +  2r  —  (3 d  +  o.oio  inch). 
As  the  depth  of  the  tooth  is 
usually  very  slight,  the  throat 
diameter    B    will    be    accurate 
enough  for  all  practical  purposes 
for  calculating  the  pitch,  and  it 
Fig.  45.  Concave  Knurl  js  not  necessary  to   take  into 

consideration  the  pitch  circle.  For  example,  assume  that  the 
pitch  of  a  knurl  is  32,  that  the  throat  diameter  B  is  0.5561 
inch,  that  the  radius  R  of  the  piece  to  be  knurled  is  JQ  inch, 
and  that  the  angle  of  the  teeth  is  90  degrees;  find  the  dimen- 
sions of  the  knurl.  Using  the  notation  given: 

/>=-  =  —  =  0.03125  inch; 


d  =  0.0156  inch; 
i     .   0.0156 


Y   —  


=  0.0703  inch; 


C  =  0.0703  +  0.0156  =  0.0859  inch; 

A  =  0.5561  +  0.1406  -  (0.0468  +  o.oio)  =  0.6399  inch. 

Spiral  Knurls.  —  When  a  knurl  has  spiral  or  helical  teeth, 
the  number  of  teeth  around  the  circumference  may  be  deter- 
mined as  follows:  Divide  the  normal  pitch  of  the  teeth  or  the 
shortest  distance  between  adjacent  rows  of  teeth  by  the 
cosine  of  the  angle  between  the  teeth  and  axis  of  the  knurl, 


KNURLING  TOOLS  147 

thus  obtaining  the  pitch  of  the  teeth  as  measured  circum- 
ferentially;  the  circumference  of  the  knurl  is  then  divided 
by  this  circumferential  pitch  to  obtain  the  number  of  teeth 
in  the  knurl.  To  illustrate,  if  the  normal  circular  pitch  is 
0.0455  inch,  and  if  the  angle  between  the  teeth  and  the  axis 
of  the  knurl  equals  30  degrees,  the  circumferential  pitch  will 
equal  0.0455  ~=~  cos  3°  degrees  =  0.0525.  The  circumference 
divided  by  0.0525  inch  will  equal  the  number  of  teeth  around 
the  circumference  of  the  knurl. 

To  find  the  lead  of  the  helix  or  spiral,  multiply  the  circum- 
ference of  the  knurl  by  the  cotangent  of  the  angle  between 
the  axis  of  the  knurl  and  the  teeth.  If  the  circumference  equals 
2.362  inches,  and  the  circular  pitch  is  0.0525  inch/ the  number 
of  teeth  equals  2.362-7-  0.0525  =  45  teeth.  If  the  angle  be- 
tween the  teeth  and  the  axis  of  the  knurl  is  30  degrees,  the  lead 
of  the  tooth  groove  or  spiral  equals  2.362  X  cot  30  degrees  =4.09 
inches,  which  represents  the  lead  for  which  the  milling  machine 
would  be  geared  when  cutting  the  knurl  teeth. 


CHAPTER  V 

ADJUSTING    OR   SETTING-UP   AUTOMATIC    SCREW 
MACHINES 

THE  automatic  screw  machine,  like  automatic  machine  tools 
in  general,  requires  first  a  set  of  cutting  tools  that  is  suitable 
for  the  particular  work  to  be  produced  and,  in  addition,  a 
certain  amount  of  adjustment,  so  that  the  movements  of  the 
different  tools  will  occur  in  the  required  order  or  sequence. 
As  the  tool  movements  are  ordinarily  controlled  by  cams, 
setting-up  or  adjusting  a  screw  machine  involves  setting  the 
cams  as  well  as  the  tools  and  whatever  additional  parts  of 
the  machine  must  operate  in  accordance  with  the  nature  of 
the  work.  On  some  automatic  screw  machines,  the  cams  are 
previously  laid  out  and  milled  to  the  exact  contour  or  shape 
necessary  for  moving  the  tools  the  required  amount  and  at  a 
suitable  rate  of  feed;  these  cams,  which  are  special  for  each 
job,  are  then  placed  on  the  machine  in  such  positions  that  the 
tools  which  they  control  act  at  the  right  time,  as  determined 
by  the  successive  order  of  the  operations.  Other  types  of  screw 
machines  are  so  designed  that  special  cams  for  each  job  are 
not  needed,  because  the  machine  can  be  adjusted  for  varying 
the  feeding  movements  and  the  time  at  which  the  different 
tools  operate.  The  following  general  information  on  screw 
machine  adjustment  applies  to  several  well-known  designs 
and  indicates  what  changes  are  necessary  for  adapting  these 
machines  to  the  production  of  different  parts. 

Setting-up  the  Brown  &  Sharpe  Machine.  —  The  cams  which 
control  the  movements  of  the  Brown  &  Sharpe  machine  are 
made  special  for  each  job,  and  the  laying  out  of  these  cams 
is  often  referred  to  as  "  camming  the  machine."  The  outline 
of  each  cam  is  plotted  on  paper  in  advance,  and  this  work 
can  be  facilitated  by  the  application  of  a  cam  templet  for  lay- 

148 


ADJUSTMENT   OF   BROWN  &   SHARPE  MACHINE  149 

ing  out  the  rise  and  drop  on  the  cam  lobes  for  various  speeds. 
In  connection  with  this  work,  it  is  necessary  to  consider  the 
speed  at  which  the  spindle  is  to  be  operated;  the  best  method 
of  producing  the  piece;  and  the  feeds  for  the  various  opera- 
tions. In  order  to  avoid  confusion,  the  actual  methods  of 
designing  cams  have  been  treated  separately  in  Chapter  VII. 

After  the  machine  is  equipped  with  the  proper  cams  for 
operating  the  turret-slide  and  the  cross-slides,  setting-up  the 
machine  is  a  comparatively  simple  operation.  The  selection 
of  the  right  feeds  and  speeds  for  the  work  is  done  in  advance 
in  connection  with  the  laying  out  of  the  cams.  In  addition 
to  making  the  adjustments  common  to  hand-operated  machines, 
it  is  simply  necessary  to  put  on  the  three  cams  which  control 
the  movements  of  the  two  cross-slides  and  the  turret-slide, 
respectively,  select  the  specified  change-gears,  and  set  the 
adjustable  dogs  which  control  the  time  of  indexing,  feeding 
of  stock,  etc.,  to  trip  at  the  proper  time.  The  cams  are  defi- 
nitely located  by  pins.  If  the  record  of  speeds,  change-gears 
used,  and  name  of  the  part  for  which  the  cams  were  designed, 
are  stamped  upon  the  side  of  one  of  the  cams,  it  is  an  easy 
matter  to  duplicate  the  work  for  which  the  cams  were  designed, 
at  any  future  time,  by  simply  equipping  the  machine  with 
the  same  cams  and  gears  previously  used. 

When  arranging  and  adjusting  the  tools,  the  most  simple 
tools  should,  generally,  be  set  first.  As  a  rule,  these  are  the 
circular  form  and  cut-off  tools  which  are  held  on  the  cross- 
.slides.  Before  any  of  the  tools  are  set,  however,  the  collet  and 
feed  finger  should  be  changed  for  the  size  of  work  required, 
the  proper  change-gears  put  on,  and  the  driving  belt  placed 
on  the  required  step.  After  the  feed  finger  and  spring  collet 
have  been  put  in  place,  the  stock  is  inserted  and  pushed  out 
far  enough  so  that  it  can  be  faced  off  with  the  circular  cut-off 
tool. 

Setting  Circular  Form  and  Cut-off  Tools.  —  The  cut-off 
tool  is  then  clamped  to  the  toolpost  and  set  with  its  cutting 
edge  as  close  as  possible  to  the  height  of  the  center  of  the  work. 
The  spindle  is  rotated  and  the  end  of  the  stock  faced  off, 


SETTING-UP   SCREW  MACHINES 


using  lever  K2,  Fig.  i,  to  operate  the  cross-side.  The  illus- 
tration shows  an  operator  setting  the  cutting  edge  of  a  circu- 
lar form  tool  to  the  height  of  the  center  of  the  work  by  means 
of  the  adjusting  nut  L%.  Care  should  be  taken  in  setting  the 
circular  form  and  cut-off  tools,  so  that  they  will  form  the  work 
parallel  and  cut  it  off  with  a  square  face.  This  is  accom- 
plished by  means  of  the  adjusting  screws  a  in  the  rear  of  the 
toolpost,  which  can  be  adjusted  when  nut  K$  is  slackened 
slightly. 


Fig.  1.   Operator  setting  a  Circular  Form  Tool 

In  setting  the  tool  on  the  front  cross-slide,  the  cutting  edge 
should  never  be  below  the  center  of  the  work,  but  should  be 
set  preferably  above  or  at  the  height  of  the  center.  The  cutting 
edge  of  the  tool  on  the  rear  cross-slide  should  be  set  just  the 
reverse  in  reference  to  the  center  of  the  work,  when  the  latter 
is  running  forward.  When  the  work  is  running  backward, 
the  position  of  the  cutting  edges  of  the  tools  on  the  front  and 
rear  cross-slide  should  be  reversed  from  that  for  the  forward 


ADJUSTMENT   OF   BROWN  &   SHARPE   MACHINE  151 

rotation  of  the  work.  If  the  cutting  edges  of  the  circular  tools 
are  not  set  in  the  positions  described,  the  work,  when  rotat- 
ing, has  a  tendency  to  pull  them  around,  thus  increasing  the 
diameter  of  the  work,  and  causing  chattering. 

When  the  circular  form,  tool  is  used  for  finishing  the  work 
to  an  exact  diameter,  the  set-screw  C3  should  always  be  set 
so  that  it  will  come  in  contact  with  the  stop  Z}3,  when  the  work 
is  turned  to  the  desired  diameter.  In  setting  this  stop,  it  should 
be  so  adjusted  that  it  will  put  a  slight  strain  on  the  cross- 


Mathinerj/ 


Fig.  2.   Simple  Method  for  Setting  a  Stock  Stop 

slide  operating  lever.  The  resulting  action  keeps  the  roll  in 
close  contact  with  the  cam,  and  thus  assures  the  parts  formed 
being  of  the  same  diameter.  When  the  circular  form  tool 
wears  slightly,  the  set-screw  C$  can  be  adjusted  back  a  slight 
amount,  and  the  strain  which  has  been  set  up  in  the  lever 
will  allow  the  tool  to  turn  the  work  to  the  desired  diameter. 
The  cross-slide  is  adjusted  back  and  forth  to  bring  the  cross- 
slide  tools  in  contact  with  the  work  by  means  of  split  nut  A, 
which  is  locked  by  means  of  a  screw.  Gib  Q5  should  be  adjusted 
so  that  there  will  be  no  unnecessary  side  play  of  the  cross- 
slide  in  the  bed. 


152 


SETTING-UP   SCREW  MACHINES 


Setting  the  Stop.  —  When  the  circular  cut-off  tool  has  been 
set  correctly,  the  chuck  is  opened  by  lifting  the  tripping  lever, 
and  the  stock  is  fed  out  the  desired  length  by  hand ;  this  length 
can  be. easily  measured  off  by  the  method  shown  in  Fig.  2. 
A  flexible  scale,  the  length  of  which  depends  upon  the  size  of 
the  machine,  is  placed  in  an  empty  hole  in  the  turret  and 
brought  up  against  the  inside  face  of  the  circular  cut-off  tool. 
The  cut-off  tool  is  now  brought  up  against  the  work  by  means 
of  the  handle  operating  the  cross-slide.  It  is  then  an  easy  mat- 
ter to  set  the  stock  to  the  desired  length.  When  this  has  been 
done,  the  chuck  is  closed  and  the  turret  swung  around  so  that 
the  stop  comes  in  line  with  the  stock. 
When  the  stop  is  in  this  position,  the 
roll  should  be  on  the  quick  rise  of  the 
lead  cam  so  that,  by  rotating  the  cam, 
the  roll  will  rise  up  onto  the  lobe,  thus 
forcing  the  stop  back  into  the  turret  the 
required  amount,  where  it  can  be  locked 
with  the  lock-screw  provided  for  that 
purpose. 

When  it  is  necessary  to  have  the 
length  of  the  piece  to  within  a  limit 
of  o.oio  inch  or  less,  the  stop  A  gives  considerable  trouble, 
because  the  only,  way  in  which  it  can  be  set  is  by  tapping 
it  in  or  out,  which  is  a  rather  difficult  matter.  A  stop  which 
gives  better  results  is  shown  at  B.  The  parts  a,  b,  and  c  are 
made  from  machine  steel  and  casehardened.  The  body  a  is 
drilled  and  tapped  for  a  screw  the  diameter  of  which  is  made 
in  accordance  with  the  size  of  the  machine  in  which  the  stop 
is  to  be  used  :  For  the  No.  oo,  d  =  T5^  inch;  for  the  No.  o,  d  = 
f  inch;  and  for  the  No.  2,  d  =  ^  inch. 

For  the  No.  oo  machine,  the  number  of  threads  per  inch  of 
the  screw  should  be  thirty-two,  which  means  that  one  revolu- 
tion would  give  an  adjustment  of  0.031  inch.  For  the  other 
machines,  the  screw  should  have  twenty  threads  per  inch. 
The  stop  proper,  b,  is  made  of  hexagonal  stock  to  fit  the  stand- 
ard wrenches  supplied  with  the  machines.  The  nut  c  is  made 


.__£ 

ORILL^ 

1 

"\ 

-GAGE 

h  DRILL 
HOLDER. 

Machinery 

Fig.  3.   Gage  for  Setting  a 
Drill 

ADJUSTMENT    OF    BROWN    &    SHARPE    MACHINE  153 


of  the  same  shape  and  from  the  same  size  of  stock  as  b.  By 
having  the  stop  hexagonal,  as  shown,  it  is  an  easy  matter  to 
set  it  within  0.005  inch,  by  means  of  the  faces  on  stop  b,  as 
the  relation  of  these  faces  to  the  nut  can  be  noted,  provided 
the  latter  is  held  with  a  wrench  while  part  b  is  rotated. 

Setting  a  Hollow  Mill  or  Box-tool.  —  In  setting  a  box-tool, 
the  bar  should  project  out  of  the  spring  collet  only  far  enough 
for  the  machining  operation,  as  otherwise  the  work  will  not 


Fig.  4.    Method  of  Operating  Machine  by  Hand  when  Making  Adjustments 

be  held  rigidly,  and  will  spring  away  from  the  cutting  tool. 
The  cutting  tool  is  first  set  to  turn  the  work  to  within  about 
0.0005  or  o.coi  inch  of  the  finished  diameter;  then  the  sup- 
ports are  forced  up  tightly  into  contact  with  the  work  and 
clamped.  It  will  be  found  that,  when  the  stock  is  fed  out  to 
the  desired  length,  the  supports  bearing  against  the  work 
tightly,  the  tool  turns  it  slightly  smaller  in  diameter.  The  box- 
tool  cutter  is  brought  in  contact  with  the  work  by  means  of 
the  handle  K^  Fig.  i,  on  the  No.  oo  machine,  and  by  the  lever 
R5  on  the  Nos.  o  and  2  machines,  as  shown  in  Fig.  7.  These 


154  SETTING-UP   SCREW  MACHINES 

levers  should  always  be  removed  before  engaging  the  driving 
clutch. 

Setting  Centering  Tools  and  Drills.  —  When  the  drill  used 
is  less  than  f  inch  in  diameter,  and  is  to  pass  entirely  through 
the  work,  a  centering  or  spotting  drill  should  always  be  used. 
The  centering  tool  should  be  ground  and  set  so  that  it  will 
not  leave  a  teat  in  the  work.  It  should  also  have  an  included 
angle  less  than  that  used  on  the  drill.  To  set  the  centering 
tool,  the  holder  carrying  the  tool  is  placed  in  the  turret,  the 
latter  swung  down,  the  spindle  stopped,  and  the  centering  tool 
brought  in  contact  with  the  work.  The  lead  cam  is  then 
rotated  by  handwheel  V&,  Fig.  4,  until  the  roll  rises  up  on  to 
the  starting  point  of  the  lobe  for  feeding  the  centering  tool 
into  the  work.  The  holder  is  tapped  back  into  the  turret,  so 
that  the  point  of  the  tool  just  clears  the  end  of  the  work; 
then  the  holder  is  clamped  in  the  turret.  If,  upon  trial,  it 
is  found  that  the  centering  tool  does  not  project  in  to  the 
required  distance,  it  is  a  simple  matter  to  bring  it  out.  The 
procedure  given  for  setting  the  centering  tool  also  applies  to 
setting  a  drill. 

It  is  advisable  to  have  a  number  of  ground  drills  on  hand, 
and  to  use  a  gage  for  setting  the  drills,  as  shown  in  Fig.  3. 
This  gage  is  made  from  sheet  steel  about  iV  inch  thick.  The 
dimension  A  is  made  equal  to  the  distance  that  the  drill  is 
required  to  extend  out  of  the  holder.  If  there  is  more  than 
one  drill  in  the  turret,  which  would  be  necessary  when  a  deep 
hole  is  to  be  produced,  a  gage  of  this  kind  should  be  made  for 
setting  each  drill.  These  gages  should  be  marked  according 
to  the  position  that  the  drill  for  which  they  are  used  takes 
in  relation  to  the  other  drills;  that  is,  "ist,"  "2nd,"  etc.,  and 
kept  in  the  same  box  as  the  other  tools  used  on  the  job.  If 
this  precaution  is  taken,  no  time  will  be  lost  in  setting  a  drill, 
because  the  machine  need  not  be  stopped. 

Setting  Counterbores  and  Reamers.  —  A  counterbore  .pro- 
vided with  a  leader  should  always  be  held  in  a  floating  holder. 
Before  setting  the  counterbore,  the  hole  should  be  drilled;  then 
the  procedure  for  setting  centering  tools  should  be  followed, 


ADJUSTMENT   OF   BROWN   &    SHARPE    MACHINE          155 

except  that  the  leader  is  inserted,  bringing  the  face  of  the 
counterbore  in  contact  with  the  end  of  the  work.  Reamers 
which  are  to  produce  deep  holes  should  be  held  in  floating 
holders. 

Setting  Dies  and  Taps.  —  Before  a  die  or  tap  and  its 
holder  are  placed  in  the  turret,  the  dogs  should  be  set  in  posi- 
tion to  reverse  the  spindle  in  the  correct  relation  to  the  thread- 
ing lobe  on  the  lead  cam.  The  two  parts  of  clutch  M  (see 
Fig.  i,  Chapter  II)  should  first  be  engaged,  so  that  the  shaft 
carrying  the  disk  on  which  the  dogs  are  located  will  be  rotated 
in  step  with  the  other  driving  mechanism  of  the  machine.  Then 


FACE  OF  WEX 


Machinery 


Fig.  5.  Turret-slide  Operating  Mechanism  on  Brown  &  Sharpe  Machine 

the  shifter  is  pulled  over  and  the  main  spindle  started.  The 
lead  cam  is  now  rotated  by  means  of  handwheel  F5,  Fig.  4, 
the  operator  also  pressing  his  thumb  against  the  turret-slide 
and  bearing  on  the  turret  base.  While  rotating  the  handwheel 
F5,  notice  when  the  spindle  reverses;  and  by  keeping  the 
thumb  in  contact  with  the  turret-slide  one  can  tell  when  the 
roll  drops  over  the  highest  point  of  the  lobe  on  the  cam.  When 
the  spindle  reverses  at  the  same  instant  that  the  roll  drops 


156 


SETTING-UP    SCREW   MACHINES 


—  REAR  CROSS- SLIDE 


c 

-—SQUARE 


over  the  highest  point  of  the  lobe  on  the  cam,  the  dog  is  set 
in  the  desired  position.  This  is  illustrated  graphically,  for 
setting  a  die,  in  Fig.  5.  'A  button  die,  held  in  a  holder,  is  shown 
in  position  ready  to  start  on  the  work.  The  face  of  the  die 
should  be  set  the  distance  A  from  the  end  of  the  work.  This 
distance  varies  from  tV  to  -3^  inch,  depending  upon  the  pitch 
of  the  thread  and  the  length  of  the  threaded  portion.  The 
detail  view  to  the  right  shows  the  cam  roll  set  just  back  of  the 

highest  point  of  the  lobe; 
when  the  roll  is  at  this 
point,  the  spindle  should 
reverse. 

After  the  first  setting,  if 
it  is  found  that  the  die  does 
not  travel  onto  the  work 
far  enough,  the  holder  is 
brought  further  out  of  the 
turret.  The  same  procedure 
is  followed  in  setting  a  tap, 
except  that  it  should  be  set 
more  carefully,  only  going 
into  the  work  a  slight  dis- 
tance when  starting,  and 
the  holder  moved  out  of 
the  turret  until  the  desired 
depth  is  reached.  It  is  sometimes  found  necessary,  after 
setting  the  tripping  dogs,  to  adjust  them  slightly,  especially 
when  using  the  drawout  type  of  die  or  tap-holder.  The  turret 
should  not  be  indexed  until  the  die  or  tap  is  clear  of  the 
work. 

Setting  Swing  Tools  and  Taper-turning  Tools.  —  Swing 
tools  are  used  for  both  internal  and  external  cutting,  and  are 
operated  under  three  different  conditions:  i.  The  cutting 
tool  is  fed  into  the  work  from  the  cross-slide  alone.  2.  The 
cutting  tool  is  fed  longitudinally  by  the  turret.  3.  The  cutting 
tool  is  fed  inward  by  the  cross-slide  and  longitudinally  by  the 
turret.  For  the  first  condition,  the  raising  block  need  not  be 


Machinery 


Fig.  6.   Use  of  a  Square  for  Setting  Raising 
Block 


ADJUSTMENT   OF   BROWN  &   SHARPE  MACHINE  157 

set  in  any  particular  relation  to  the  axis  of  the  spindle.  When 
straight  turning  is  to  be  produced  under  the  second  condition, 
the  face  of  the  raising  block  should  be  set  parallel  with  the 
axis  of  the  spindle.  For  the  third  condition,  when  the  work 
is  to  be  turned  taper,  the  face  of  the  raising  block  should  be 
set  at  an  angle  with  the  axis  of  the  spindle. 

In  Fig.  6  is  shown  a  simple  method  of  setting  the  face  of  the 
raising  block  parallel  with  the  axis  of  the  spindle.  An  ordinary 
adjustable  square  is  held  against  the  face  of  the  rear  cross- 
slide,  and  screw  A  is  adjusted  until  the  block  is  set  correctly, 


Fig.  7.   Testing  Position  of  Raising  Block  by  means  of  Dial  Indicator 

after  which  screw  B  is  tightened.  This  method  can  be  used 
when  it  is  not  necessary  to  have  the  raising  block  set  exactly 
parallel  with  the  axis  of  the  spindle. 

A  better  and  more  accurate  method  is  shown  in  Fig.  7. 
Here  a  dial  test  indicator  B  is1  used.  A  split  bushing  is  inserted 
in  one  of  the  holes  in  the  turret,  and  a  bent  rod  with  the  indi- 
cator is  held  in  it.  The  finger  of  the  indicator  is  brought  to 
bear  against  the  face  of  the  raising  block  C,  and  the  turret  is 
traversed  by  handle  R$  on  the  Nos.  o  and  2  machines,  and  by 
using  handle  K^  Fig.  i,  on  the  No.  oo  machine,  inserting  it 
in  the  turret  traversing  lever.  While  the  turret  is  being  trav- 
ersed back  and  forth,  the  movement  of  the  needle  on  the  dial 
is  noted,  and  the  screw  A  adjusted  until  no  movement  is 
transmitted  to  the  needle. 


158  SETTING-UP    SCREW   MACHINES 

The  setting  of  the  raising  block  for  operating  a  taper  turn- 
ing tool  or  a  swing  tool  for  taper  turning  is  generally  done  by 
the  cut-and-try  method,  the  first  time  the  tools  are  set  up. 
Most  operators,  when  setting  up  a  job  for  the  second  time,  use 
what  is  called  a  "  set  piece"  to  set  the  tools  by.  This  is  a  piece 
of  work  which  has  been  made  correctly  to  size,  but  which  is 
not  entirely  cut  off,  as  shown  at  C  in  Fig.  6.  It  is  gripped  in 
the  collet,  and  the  turning  tool  as  well  as  the  circular  form  and 
cut-off  tools  are  set  to  it. 

General  Method  of  Setting-up  Screw  Machine.  —  To  illus- 
trate the  method  followed  in  setting-up  a  Brown  &  Sharpe 
automatic  screw  machine,  let  it  be  assumed  that  a  set  of  cams 
as  illustrated  in  Fig.  8  have  been  designed  and  made  for  pro- 
ducing a  button-head  screw  on  the  No.  oo  machine.  These 
cams,  together  with  the  special  and  standard  tools  which  are 
numbered,  are  turned  over  to  the  operator.  He  also  receives 
a  drawing  similar  to  that  shown  in  Fig.  8.  Assume  that  the 
machine  has  been  set  up  for  another  piece  of  work,  so  that 
it  is  necessary  to  dismantle  it.  The  operator  first  removes 
all  the  tools  from  the  turret  and  the  cams  from  the  front  and 
rear  end  shafts.  He  also  removes  the  spring  collet  by  removing 
the  cap,  and  the  feed- tube  by  lifting  the  latch;  then  he  unscrews 
the  feed  finger,  which  is  threaded  left-hand.  The  change- 
gears  are  now  removed,  leaving  the  machine  dismantled  ready 
for  the  new  job. 

To  proceed,  the  operator  first  inserts  the  spring  collet,  puts 
on  the  cap,  and  then  screws  the  new  feeding  finger  into  the 
feed-tube,  and  inserts  the  latter  into  the  spindle.  He  then 
puts  the  stock  into  the  feed-tube,  and  places  a  suitable  pipe 
in  the  stand  in  which  the  stock  is  to  revolve.  This  pipe  should 
be  central  with  the  feed-tubes,  thus  reducing  the  wear  in  the 
hole  of  the  latter.  The  belts  are  now  placed  on  their  proper 
cones  to  give  the  desired  spindle  speeds.  All  belts  should  be 
without  rivets,  and  preferably  should  be  laced  with  wire,  as 
this  gives  a  smoother  running  belt.  All  the  bearings  should 
be  oiled  with  good  machinery  oil,  and  also  the  friction  clutch. 
The  latter  should  be  oiled  at  least  twice  a  day. 


ADJUSTMENT  OF  BROWN  &   SHARPS  MACHINE  159 


160  SETTING-UP   SCREW  MACHINES 

After  the  belts  have  been  placed  on  the  proper  cones,  the 
collet,  feed  finger,  etc.,  having  been  inserted,  the  change- 
gears  should  be  put  in  place.  The  handwheel  is  next  put  or 
for  operating  the  machine  by  hand.  Before  putting  on  the 
cams,  set  the  collet  so  that  it  has  the  proper  grip  on  the  stock ; 
then  open  the  collet  again  and  push  the  stock  out  far  enough 
to  be  faced  off  by  the  cut-off  tool.  After  closing  the  collet, 
start  the  spindle  and  set  the  cross-slide  circular  form  and  cut- 
off tools  at  the  height  of  the  center  of  the  work,  and  in  their 
proper  relation  to  each  other.  Next  put  on  the  front  and  rear 
cross-slide  cams,  and  if  the  job  requires  a  threading  operation, 
as  in  this  case,  the  shaft  with  the  drum  carrying  the  tripping 
dogs  for  reversing  the  spindle  should  be  connected  with  the 
front  camshaft. 

Next,  set  in  the  cross-slides  by  adjusting  nuts  A3,  Fig.  i, 
so  that  the  circular  form  and  cut-off  tools  travel  in  to  the  re- 
quired distance.  Place  the  hollow  mill  in  the  turret,  set  it 
correctly,  and  also  set  the  tripping  dog  so  as  to  revolve  the 
turret.  Put  the  box-tool  in  the  turret,  set  it,  and  also  set  the 
dog  for  indexing  the  turret.  The  die  is  then  set  as  previously 
described,  and  all  the  tripping  dogs  are  set  to  index  the  turret 
completely  around.  After  all  the  tools  have  been  set  in  their 
proper  relation,  make  a  piece,  except  threading,  by  turning 
the  handwheel;  at  the  threading  operations,  drop  down  the 
die  so  that  it  does  not  pass  onto  the  work.  Gage  the  piece 
thus  made;  if  it  is  correctly  to  size,  and  the  tripping  dogs  for 
reversing  the  spindle  and  the  die  have  been  properly  set, 
throw  the  feed  clutch  by  means  of  handle  P  (Fig.  i,  Chapter 
II)  and  start  the  machine. 

When  the  bar  is  all  used  up,  the  chuck  should  be  opened 
by  tripping  the  lever,  and  the  turret  revolved  by  withdrawing 
the  locking  pin,  so  that  it  will  not  interfere  with  the  short  piece 
left  in  the  chuck,  which  should  be  driven  out  for  the  inser- 
tion of  a  new  bar.  To  insert  the  new  bar,  turn  the  handwheel 
sufficiently  to  bring  the  shoulder  of  the  feed-tube  against  the 
end  of  the  spindle,  and  push  out  the  bar  just  far  enough  so 
that  its  front  end  can  be  faced  off  with  the  cut-off  tool.  Now 


ADJUSTMENT  OF  CLEVELAND  MACHINE 


161 


turn  the  turret  back  into  position  and  start  the  machine  by 
throwing  in  the  clutch.  The  ends  of  the  rods  of  stock  should 
be  ground  to  remove  the  burrs,  thus  insuring  their  entering 
and  feeding  freely  and  evenly  through  the  feed- tube.  The 
work  should  always  be  tested  after  the  insertion  of  a  new  bar 
of  stock.  If  the  parts  made  are  short  or  thin,  the  tools  will 
become  dull  much  more  quickly;  consequently,  the  work 
should  be  tested  more  frequently  in  that  case,  so  that  any 
errors  may  be  corrected  as  soon  as  possible. 

Adjusting  the  Cleveland  Automatic  Machine.  —  The  setting- 
up  of  a  Cleveland  automatic  screw  machine  is  principally  a 


Fig.  9.   Turret-slide  of  Cleveland  Automatic,  which  is  Adjusted  Along  the  Bed  to 
Suit  the  Various  Lengths  of  Work  and  Turret  Tools 

matter  of  adjusting  the  cams  on  the  cross-slide  drum,  as  well  as 
the  cams  controlling  the  variable  tool  feed  and  the  stock  feed. 
Assuming  that  all  the  tools  and  other  equipment  that  have 
been  used  on  previous  jobs  have  been  removed,  the  first  step  is 
to  insert  the  chuck.  The  hood  on  the  nose,  of  the  spindle  is 
first  removed  by  a  spanner  wrench,  and  the  chuck  is  then  in- 
serted, care  being  taken  to  remove  all  chips  and  heavy  oil 
which  would  retard  its  action.  When  the  chuck  is  of  the  pad 
type,  it  is  only  necessary  to  remove  the  pads  and  replace  them 
by  those  suited  to  the  size  of  the  stock  that  is  to  be  handled. 
After  putting  the  chuck  in  place,  the  feed-tube  is  then  taken 
out  and  the  desired  size  of  shell  or  pads  inserted.  After 


1 62  SETTING-UP   SCREW  MACHINES 

putting  the  chuck  and  feed-tube  in  place,  the  chuck  is  then 
closed  by  hand  and  the  cross-slide  tools  are  placed  in  their  ap- 
proximate positions,  allowing  about  f  inch  clearance  between 
the  front  face  of  the  chuck  and  the  inner  face  of  the  cutting-off 
or  forming  tools. 

Adjusting  the  Turret  Head.  —  Following  the  insertion  of 
the  chuck  and  feed-shell,  the  next  move  is  to  adjust  the  turret 
head  A  (Fig.  9)  along  the  bed  to  accommodate  the  length  of 
work  to  be  turned.  This  adjustment  is  made  by  turning 
screw  B.  The  turret  should  be  advanced  to  full  stroke,  that 
is,  to  its  extreme  forward  position,  by  means  of  shaft  C  oper- 
ated by  the  same  crank  handle  that  adjusts  screw  B,  and  the 
turret  tool  having  the  greatest  body  length  should  be  used 
in  determining  the  position  of  the  turret  head  on  the  bed.  In 
making  this  adjustment,  the  clamping  screws  which  fasten 
the  turret  head  to  the  bed  should  be  released;  one  of  these 
screws  is  shown  at  D  and  the  other  is  at  the  front  end  of  the 
turret  head  underneath  the  bed.  These  should  be  securely 
tightened  when  the  turret  head  is  in  the  desired  position. 

Setting  the  Turret  Tools.  —  Turning  our  attention  now  to 
the  turret,  the  first  tool  to  be  set  is  the  gage  stop.  This  is  used 
for  gaging  the  stock  to  the  correct  length  and  should  be  set 
in  relation  to  the  cut-off  tool.  The  proper  procedure  is  to 
measure  from  the  outside  face  of  the  cut-off  tool  to  the  front 
face  of  the  gage  stop,  when  the  turret  is  advanced  to  its  ex- 
treme forward  position.  All  the  other  tools  are  then  placed 
in  the  turret  in  their  proper  holes.  In  setting  the  turret  tools, 
the  exact  length  required  for  the  job  is  secured  by  measuring 
from  the  face  of  the  gage  stop  to  the  cutting  tool,  or  from 
the  outer  face  of  the  cut-off  tool  to  the  front  edge  of  the  cut- 
ting tool,  with  the  turret  advanced  to  its  extreme  forward 
position,  as  before.  No  attention  is  given  to  the  final  setting 
of  the  cutters  in  a  box-tool,  until  all  the  tools  have  been  set 
in  their  proper  relative  positions. 

Adjusting  Cross-slide  Operating  Cams.  —  The  cams  for 
operating  the  cross-slide  are  of  curved  segment  form  and  are 
held  on  a  drum  F  shown  in  Fig.  10.  The  procedure  in  setting 


ADJUSTMENT    OF    CLEVELAND   MACHINE  163 

these  cams  is  to  first  advance  the  turret  E  to  its  full  outward 
stroke  and  then  bring  the  cross-slide  by  hand  to  the  approxi- 
mate position  that  the  forming  tool  will  occupy  when  it  has 
finished  taking  a  cut.  The  bellcrank  lever  G  is  then  moved 
until  the  roll  touches  the  flange  of  the  cam  drum,  and  a  mark 
is  made  with  a  lead  pencil,  indicating  the  position  of  the  roll 
on  the  surface  of  the  drum.  Then  the  machine  is  operated 
again  by  hand,  rotating  the  drum  about  one-half  turn,  and  the 
high  point  of  the  forming  cam  H  is  placed  so  that  it  coin- 


Fig.  10.  Cams  on  Cross-slide  operating  Drum,  which  are  moved 
around  to  the  Required  Position  and  Clamped  by  Cap-screws 

cides  with  the  circumference  of  the  circle  previously  outlined. 
The  cam  for  operating  the  cut-off  tool  is  located  in  the  same 
manner,  and  is  generally  the  last  to  be  set. 

The  relief  cams  /  (only  one  of  which  is  shown)  that  draw 
the  cross-slide  to  a  central  position,  after  the  forming  and 
cut-off  tools  have  finished  their  operations,  are  next  adjusted. 
The  cap-screws  fastening  these  cams  to  the  drum  F  are  re- 
leased, and  the  cams  are  shifted  around  so  that  the  high  points 
contact  with  the  roll  and  hold  the  slide  in  the  central  position, 
after  which  the  cams  are  clamped,  to  the  drum. 


164 


SETTING-UP    SCREW   MACHINES 


The  cross-slide  connecting-rod  which  controls  the  exact  posi- 
tion of  the  cross-slide  is  adjusted  as  required  by  the  move- 
ment of  the  forming  and  cutting-off  tools.  Two  adjusting 
nuts  provided  with  individual  locking  nuts  are  located  on  this 
connecting-rod,  and  these  are  adjusted  back  and  forth  in  rela- 
tion to  the  central  pin  in  the  bellcrank  lever  G,  in  order  to 
carry  the  slide  to  its  exact  position.  After  making  this  adjust- 
ment of  the  cross-slide,  the  machine  should  be  turned  one 


Fig.  11.  Adjustment  of  Belt-shifter  Dogs  for  Controlling  Speed  and 
Direction  of  Spindle  Rotation 

complete  cycle  by  hand,  in  order  to  insure  the  operator  that 
each  tool  has  been  properly  placed. 

Making  the  Speed  Changes.  —  The  next  point  that  requires 
attention  is  the  correct  spindle  speed  to  use.  This  is  governed 
largely  by  the  material  that  is  to  be  operated  upon,  and  to 
some  extent  by  the  tools  that  are  to  perform  the  operations. 
Fig.  ii  illustrates  the  method  of  adjusting  the  belt-shifter  dogs 
to  obtain  the  different  spindle  speeds  required  to  suit  the  tools 
that  have  been  placed  in  position.  When  a  job  is  to  be  threaded 


ADJUSTMENT   OF    CLEVELAND   MACHINE  165 

with  a  spring  or  button  die,  or  a  tap  is  to  be  used,  it  is  neces- 
sary to  set  the  reversing  dogs  to  reverse  the  spindle  exactly 
at  the  time  when  the  turret  is  at  the  full  forward  position. 

In  order  to  make  this  adjustment  without  danger  of  injuring 
the  tap  or  die,  the  bar  stock  should  be  removed  from  the 
spindle,  the  turret  advanced  by  hand  to  the  extreme  forward 
position,  and  the  belt-shifter  dog  set  to  reverse  the  spindle  at 
this  point;  then  the  turret  is  backed  up  by  hand  and  the 
power  feed  is  thrown  in,  care  being  taken  to  observe  whether 


Fig.  12.  Adjustment  of  Compression  Collar  Nut  for  Varying  the 
Gripping  Pressure  of  the  Chuck  on  the  Bar 

the  spindle  reverses  just  as  the  turret  starts  on  its  backward 
motion.  If  the  spindle  reverses  a  little  too  soon  or  a  little 
too  late,  the  belt-shifter  dog  is  adjusted  slightly  to  correct 
the  time  of  reverse.  When  it  is  seen  that  the  spindle  reverses 
exactly  at  the  moment  the  turret  starts  on  its  backward 
stroke,  the  adjustment  is  correct,  and  the  bar  stock  may  then 
be  replaced  in  the  machine  and  the  threading  die  will  cut 
correctly.  No  adjustment  of  this  kind  is  necessary  when  self- 
opening  dies  or  collapsible  taps  are  used,  because,  when  the 
thread  is  finished,  the  chasers  clear  the  work,  and  it  is  not 
necessary  to  reverse  the  spindle.  There  are  several  different 


1 66  SETTING-UP   SCREW  MACHINES 

combinations  and  arrangements  of  spindle  drives  possible  on 
the  Cleveland  automatics. 

Chucking  and  Feeding  Adjustments.  —  Assuming  now  that 
the  tools  have  been  set  in  approximately  correct  positions, 
the  next  step  is  to  place  the  bar  of  stock  in  the  spindle  of  the 
machine  and  adjust  the  chuck  to  its  proper  grip  on  the  work. 
This  is  accomplished  by  means  of  an  adjusting  nut  A  shown 


Fig.  13.   Method  of  Regulating  the  Length  of  the  Stock-feeding 
Movement 

in  Fig.  12,  which  is  located  at  the  rear  end  of  the  spindle. 
In  this  illustration,  the  operator  is  shown  turning  the  ad- 
justing nut  with  the  spanner  wrench.*  Before  adjusting  this 
nut,  it  is  necessary  to  release  the  binding  nut  B  until  compres- 
sion nut  A  is  released.  Adjusting  nut  A  is  turned  until  the 
chuck  has  sufficient  grip  on  the  work  to  prevent  it  from  being 
shifted  by  the  action  of  the  turning  tools.  When  it  is  desired 
to  tighten  the  grip  of  the  chuck,  the  adjusting  nut  A  is  turned 


ADJUSTMENT  OF  CLEVELAND  MACHINE 


I67 


toward  the  right;  turning  it  toward  the  left  loosens  the  grip 
of  the  chuck.  This  direction  is  taken  with  the  operator  facing 
the  spindle  and  standing  at  the  end  of  the  machine.  When 
the  correct  adjustment  of  the  chuck  on  the  work  is  obtained, 
the  binding  nut  B  is  tightened  to  lock  the  adjusting  nut. 
The  next  step  is  to  set  the  stock-feeding  mechanism  so  that 


Fig.  14.  Setting  the  Shifter  Pins  on  the  Regulating  Drum  so  that 
the  Feeding  Movements  and  the  High-speed  Movements  occur  at 
the  Proper  Time 

the  bar  will  be  fed  out  to  the  correct  distance.  Fig.  13  shows 
the  method  of  making  this  adjustment,  which  is  secured  by 
shifting  the  position  of  the  stock  feed-rod  head  A  along  the 
shaft  so  that  cam  H  will  engage  with  the  roll  B  at  a  point 
that  will  feed  the  stock  out  to  the  desired  length.  The  last 
J-inch  movement  of  the  stock  feed-rod  should  take  place 
after  the  chuck  is  opened.  This  will  give  time  for  the  spring 
chuck  to  open  fully  before  the  stock  starts  to  feed  to  the  gage 


1 68  SETTING-UP   SCREW  MACHINES 

stop.  The  stock-feeding  mechanism  should  be  set  to  feed 
about  %  inch  more  than  the  job  requires,  and  the  gage  stop  in 
the  turret  will  force  the  stock  back  to  the  desired  length  just 
as  the  chuck  is  closing  on  the  bar. 

Setting  the  Feed-shifting  Pins.  —  The  feed  on  the  Cleve- 
land automatic  is  changed  from  the  slow  to  the  fast  speed 
through  a  sliding  clutch.  This  is  secured  by  means  of  shifter 
pins  A  and  B  (Fig.  14)  which  are  held  in  T-slots  in  the  rear 
face  of  the  regulating  drum.  In  setting  these  feed  shifter  pins, 
each  tool  in  the  turret  is  advanced  by  hand,  so  that  it  is  brought 
to  within  about  3*2  mcn  °f  where  it  should  start  to  cut.  Then 
the  feed  shifter  pin  B  is  moved  around  in  the  T-slot  of  the  regu- 
lating drum  and  set  to  shift  the  clutch  to  the  slow  speed  at 
this  point.  In  the  case  of  a  tap  or  die,  the  tool  should  be  brought 
to  a  position  J  inch  from  the  face  of  the  work.  The  feed  shifter 
pins  A  in  the  outer  T-slot  of  the  regulating  drum  control  the 
fast  or  idle  movements  of  the  machine,  and  should  be  set  to 
shift  the  clutch  into  the  fast  speed  at  the  completion  of  each 
tooling  cut,  whereas  the  pins  B  in  the  inner  T-slot  control 
the  shifting  of  the  clutch  to  the  slow  speed  and  are  set  to  move 
the  clutch  at  the  point  previously  described. 

Adjustment  of  Feed-regulating  Drum.  —  One  of  the  impor- 
tant features  of  the  Cleveland  automatic  is  the  regulating 
drum,  which  is  used  for  securing  separate  feeds  for  each  tool 
in  the  turret  and  on  the  cross-slide,  the  feed  per  revolution  of 
the  spindle  being  controlled  by  segment  cams  which  can  be 
adjusted  while  the  machine  is  in  operation.  Fig.  15  shows 
the  setting  or  adjusting  of  the  feed  regulating  cams  7.  These 
cams  are  attached  to  the  flange  of  the  regulating  drum  by 
means  of  two  cap-screws.  The  flange  of  the  drum  is  slotted 
to  allow  adjustment  of  the  cams.  By  shifting  the  position  of 
the  cams,  any  desired  feed  can  be  secured  for  each  individual 
tool.  Moving  them  toward  the  outer  edges  decreases  the  feed, 
and  in  the  opposite  direction  increases  the  feed.  The  edges 
of  cams  /,  through  the  medium  of  a  bellcrank  lever,  guide 
the  position  of  roll  /  automatically  up  and  down  between  the 
friction  disks  K  which  drive  the  turret  drum  and  camshaft. 


ADJUSTMENT    OF    CLEVELAND    MACHINE  169 

This  makes  it  possible  to  increase  or  decrease  the  tool  feed 
as  required,  to  suit  the  material  being  cut  and  the  type  of 
tools  performing  the  operations. 

The  position  of  the  pointer  on  indicator  L  determines  the 
location  of  the  feed  regulating  cams  when  setting  up  a  job  for 
the  second  time.  The  indicator  is  held  on  an  arm  moving  up 
and  down  on  a  post;  this  arm  receives  its  motion  from  the 
bellcrank  lever  which,  in  turn,  is  operated  by  the  cams  on  the 


Fig.  15.  Adjustment  of  the  Regulating  Drum  Segment  Cams  to 
give  the  Required  Rate  of  Feed  for  the  Turret  and  Cross-slide 
Tools 

regulating  drum.  The  position  of  the  pointer  is  recorded 
on  a  record  sheet  which  should  be  filled  out  before  changing 
to  other  work,  and  used  as  a  guide  when  setting  up  the  same 
job  again.  This  record  sheet  shows  the  position  of  all  adjust- 
able cams  and  gives  all  the  necessary  tooling  data.  In  addition 
to  the  adjustments  previously  mentioned,  there  are  positive 
stops  for  the  front  and  rear  of  the  cross-slide  which  need  to  be 
set  and  which  make  extreme  accuracy  easily  obtainable.  These 
stops  are  in  the  center  of  the  slide  and  control  the  exact  posi- 
tion of  the  tools. 


170  SETTING-UP   SCREW   MACHINES 

Adjustment  of  Acme  Multiple-spindle  Machine.  —  To 
make  clear  the  methods  followed  in  setting-up  and  operating 
the  "  Acme "  automatic  multiple-spindle  screw  machine,  a 
representative  piece  will  be  taken  as  an  example,  and  the 
various  steps  to  be  followed  in  setting-up  and  operating  the 
machine  for  producing  this  piece  will  be  dealt  with  in  detail. 
While  there  are  many  questions  that  will  arise  in  setting-up 
the  machine  for  producing  various  parts,  where  actual  experi- 
ence in  work  of  a  similar  character  would  in  many  cases  elimi- 
nate the  necessity  of  experiment,  if  the  operator  has  a  general 
idea  of  the  various  working  mechanisms  of  the  machine  and 
their  relation  to  each  other,  he  will  experience  little  difficulty 
in  adjusting  the  machine  for  average  work. 

Assuming  that  the  machine  has  been  set  up  on  a  piece  of 
work,  the  first  thing  that  the  operator  does  is  to  dismantle 
those  parts,  tools,  gears,  cams,  etc.,  which  have  to  be  changed 
for  every  new  job,  leaving  any  cams  or  tools  in  position  that 
can  be  used  on  the  new  piece.  As  a  rule,  the  spring  chucks  and 
feed  chucks  are  removed  first  and  are  replaced  by  those  of  the 
proper  size  and  shape.  Then  the  tools  in  the  main  tool-slide 
and  the  side-  and  top- working  tool-slides  are  removed.  When 
a  straight  blade  cut-off  tool  is  used  in  the  cut-off  tool-slide,  it 
generally  can  be  used  for  more  than  one  job,  so  that  in  many 
cases  this  tool  need  not  be  removed.  The  cams  on  the  main 
drum,  and  also  the  cams  for  operating  the  side-working  tool- 
slides,  are  now  removed  and  replaced  by  cams  which  will  give 
the  required  amount  of  travel.  The  back-gears  for  rotating 
the  end-working  tools  and  the  threading  spindle  are  next 
removed  and  replaced  by  gears  that  will  give  the  proper  speeds 
'  for  the  work  in  hand. 

If  it  is  necessary  for  the  operator  to  proceed  without  instruc- 
tions, he  must  first  decide  on  the  best  method  of  applying 
the  tools  before  he  begins  to  set  up  the  machine.  As  this  is 
frequently  the  case,  it  may  be  advisable  to  give  a  short  de- 
scription of  some  of  the  points  which  have  to  be  taken  into  con- 
sideration when  deciding  on  the  best  method  of  tooling  the 
machine  for  producing  any  certain  part. 


ADJUSTMENT  OF  ACME  MACHINE 


Deciding  on  the  Method  of  Tooling.  —  The  four  spindles 
of  the  Acme  automatic  multiple-spindle  screw  machine  may 
tend  to  confuse  a  new  operator,  and  to  give  him  the  impression 
that  a  clear  understanding  of  the  method  of  tooling  is  more 
difficult  to  obtain  than  when  using  a  single-spindle  machine. 
The  chief  reason  for  this  is  that  all  the  tools  are  used  at  once; 


ORDER  OF  OPERATIONS 


FIRST"  POSITION 


I     "SECOND"  POSITION* 


"THIRD"  POSITION 


"FOURTH"  POSITION 


PIECE  TO  MAKE 


16  P. 


MACHINE  STEEL 


Machinery 


Fig.  16.   Successive   Operations  for  Producing  a  Hexagon-head  Cap- 
screw  on  a  Multiple-spindle  Machine 

however,  this  fact  frequently  makes  it  possible  to  rearrange 
the  tools  considerably  on  repeating  a  set-up,  and  what  might 
have  been  considered  the  best  method  of  tooling  a  certain 
piece  when  it  was  first  made  may  prove  inferior  to  the  new 


172  SETTING-UP    SCREW   MACHINES 

method.  This  possibility  of  improving  upon  the  method  of 
tooling  sometimes  changes  the  order  of  operations  to  such  an 
extent  as  to  entirely  change  the  method  of  manufacture. 

As  an  illustration,  assume  that  it  is  necessary  to  produce 
the  cap-screw  shown  in  Fig.  16,  which  is  to  be  made  from  cold- 
rolled  hexagon  steel,  {J  inch  in  " diameter"  across  the  flats. 
As  this  is  just  an  ordinary  cap-screw,  the  body  need  not  be 
shaved,  but  can  be  produced  accurately  enough  for  all  prac- 
tical purposes,  by  dividing  the  cuts  on  the  body  between 
two  box-tools,  which  are  held  in  the  end-working  tool-slide. 
The  operation  at  A,  which  takes  place  in  the  "first"  position, 
is  performed  with  a  circular  form  tool  and  box-tool.  The 
circular  form  tool  forms  the  head  and  "necks"  or  grooves 
the  piece,  whereas  the  box-tool,  held  in  the  "first"  position 
tool  spindle,  turns  one-half  the  length  of  the  body.  In  choos- 
ing the  lead  cam  for  the  forward  travel  of  the  main  tool-slide, 
a  one-inch  cam  is  sufficient,  owing  to  the  fact  that  the  two 
box-tools  are  working  on  different  bars  at  the  same  time.  The 
second  box-tool  cutter  is  set  one  inch  further  out  from  the  face 
of  the  main  tool-slide  than  the  first  box-tool  cutter,  in  order 
to  complete  the  turning  on  the  body  of  the  cap-screw. 

Calculating  the  Production  per  Hour.  —  As  all  of  the  end- 
working  tools  come  up  to  the  work  at  the  same  time,  it  follows 
that  in  most  cases  all  four  tools  from  the  end  would  be  at  work 
on  different  bars  at  the  same  time.  In  this  case,  the  screw 
only  requires  the  use  of  three  end-working  tools  —  two  box-tools 
and  a  die  —  although  a  pointing  tool  could  be  used  if  neces- 
sary to  make  the  point  on  the  screw  after  it  is  threaded.  By 
considering  the  operations  on  this  cap-screw,  it  will  be  found 
that  the  longest  operation  is  that  necessary  to  turn  one-half 
the  length  of  the  body;  then  to  find  the  production  per  hour, 
it  is  first  necessary  to  determine  the  speed  at  which  it  is  best 
to  run  the  work.  As  a  rule,  ordinary  cold-drawn  stock  can  be 
worked  at  from  65  to  75  surface  feet  per  minute  for  forming 
tools  or  box- tools.  In  this  case,  select  75  surface  feet  as  a 
suitable  speed;  then,  assuming  that  the  bar  is  round  and  of 
a  diameter  equal  to  the  distance  across  the  flats,  it  will  be 


ADJUSTMENT    OF    ACME    MACHINE  173 

found  that  a  spindle  speed  of  420  revolutions  per  minute  will 
be  about  right.  The  table  of  spindle  speeds  accompanying 
the  No.  53  machine  shows  that  445  is  the  closest  number  ob- 
tainable. As  the  speed  will  not  be  increased  excessively,  the 
back-gears  for  this  higher  speed  may  be  used. 

The  next  step  is  to  find  the  number  of  revolutions  of  the 
spindle  required  for  the  box-tool  to  travel  one  inch  along  the 
work,  at  a  certain  feed  per  revolution.  The  body  diameter  of 
this  cap-screw  is  f  inch,  while  the  diameter  across  the  corners  is 
0.794  inch,  giving  a  depth  of  cut  of  0.209,  or  approximately 
3*2  inch.  If  a  feed  of  0.004  mcn  Per  revolution  is  selected 
and  0.040  inch  allowed  for  the  tool  to  approach  the  work,  it 
will  be  found  that  it  will  take  260  revolutions  of  the  spindle 
for  the  box-tool  to  travel  the  distance  required. 

There  are  several  methods  followed  in  obtaining  the  pro- 
duction of  the  Acme  automatic  screw  machine,  one  method 
being  based  on  the  assumed  output  per  hour,  which  can  be 
obtained  by  the  following  formula: 

RX  60 

r 
in  which  P  =  assumed  product  in  pieces  per  hour; 

R  =  revolutions  per  minute  of  work-spindle; 
r  —  revolutions  of  spindle  required  to  complete  the 

longest  single  operation. 
Inserting  the  values  previously  obtained  in  this  formula: 

P  = — —       -  =  103  (approximately). 
260 

In  assuming  this  product,  the  time  required  to  feed  the 
stock,  index  the  cylinder,  etc.,  was  not  considered,  and,  in- 
stead of  calculating  the  actual  time  required  for  these  idle 
movements,  an  approximation  is  made.  Referring  to  the 
change-gear  table  for  the  machine  that  is  to  be  used,  it  will 
be  found  that  the  next  closest  production  to  103  is  98.5;  then, 
by  reducing  the  production  to  98.5  pieces  per  hour,  allow  suf- 
ficient time  to  take  care  of  the  idle  movements  of  the  machine. 

Another  method  is  to  calculate  the  time  required  for  the 


174  SETTING-UP    SCREW   MACHINES 

longest  single  operation  in  the  manner  just  described,  and  then 
determine  definitely  the  actual  time  required  to  feed  the 
stock,  index  the  cylinder,  etc.  This  is  added  to  the  time 
required  for  the  longest  single  operation,  the  sum  giving  the 
exact  time  required  to  produce  one  piece.  This  method, 
while  considerably  longer  than  the  other,  has  the  advantage 
of  working  on  a  definite  basis  and  may  be  clearly  understood 
by  those  not  entirely  familiar  with  the  construction  and  opera- 
tion of  this  machine. 

Spring  Chucks  and  Stock  Support.  —  Assuming  that  the 
machine  has  been  dismantled  and  is  to  be  arranged  for  the 
operation  shown  in  Fig.  16,  the  first  thing  to  consider  is  the 
insertion  of  the  proper  spring  chucks  and  feed  chucks  for 
feeding  and  holding  the  bars.  A  round  chuck  should  never 
be  used  for  holding  either  square  or  hexagon  stock,  but  a 
chuck  of  the  same  shape  as  the  work  should  always  be  used. 
After'  the  feed  chuck  and  spring  chuck  have  been  put  in 
place,  the  bars  of  stock  are  inserted  in  the  spindles,  the  chucks 
being  opened  and  the  bars  pushed  through,  so  that  they  ex- 
tend far  enough  out  of  the  chucks  to  allow  for  cutting  off  the 
finished  parts.  As  a  rule,  it  is  good  practice  to  put  the  bars 
of  stock  into  pipes  for  guiding  them,  before  the  machine  is 
started.  In  putting  the  stock-supporting  reel  in  place,  when 
the  bars  are  already  in  the  spindles  of  the  machine,  the  reel 
is  simply  slid  back  over  the  rear  bracket  until  it  passes  the 
end  of  the  bars,  and  is  then  pushed  forward  again,  the  bars 
passing  into  the  pipes.  A  satisfactory  method  is  to  leave  the 
reel  in  place  and  push  the  rods  through  the  pipes  into  the 
spindles,  then  slide  the  reel  back  slightly  to  facilitate  chucking, 
and  replace  it  again  in  the  running  brackets  before  starting  the 
machine.  When  the  stock  is  small  in  diameter,  the  ends  pro- 
jecting from  the  rear  end  of  the  machine  should  be  guided 
by  the  pipes  of  the  reel,  as  this  prevents  damage  to  both  the 
machine  and  the  operator,  due  to  a  slight  twist  in  the  bars 
which  causes  them  to  rotate  eccentrically  and  buckle. 

Selecting  and  Changing  the  Back-gears.  —  After  the  stock 
has  been  inserted  in  the  machine,  and  the  chucks  closed  on  it 


ADJUSTMENT  OF  ACME  MACHINE  175 

by  cranking  the  machine,  the  next  step  is  to  obtain  the  desired 
spindle  speed.  This  is  secured  by  removing  the  back-gears 
shown  in  Fig.  5,  Chapter  III,  and  replacing  them  with  the 
gears  which  will  give  the  proper  speed  for  the  work  in  hand. 
For  the  operation  shown  in  Fig.  16,  a  spindle  speed  of  445 
revolutions  per  minute  has  been  selected.  Referring  to  the 
spindle-speed  table  for  the  No.  53  machine,  it  will  be  found 
that  the  gears  should  go  on  as  follows:  A  —  52;  B  —  46; 
C  —  26;  D  — 32.  In  putting  on  the  back-gears,  see  that  they 
do  not  mesh  too  closely. 

Selecting  the  Lead  and  Forming  Cams.  —  A  feature  of  the 
Acme  automatic  screw  machine  which  should  be  borne  in  mind 
is  that  the  lead  cam,  located  on  the  drum  for  governing  the 
forward  advance  of  the  main  tool-slide,  is  not  adjustable,  but 
is  bolted  to  the  drum.  Now,  for  different  work,  these  cam  strips 
which  are  all  of  the  same  length,  but  have  different  rises,  are 
put  on  the  drum  G  (Fig.  i,  Chapter  III)  and  clamped  by 
cap-screws.  For  making  the  cap-screw  shown  in  Fig.  16,  it 
is  necessary  that  the  main  tool-slide  travel  forward  approxi- 
mately one  inch,  so  that  in  this  case  a  lead  cam  having  a  rise 
of  one  inch  in  its  length  is  selected.  To  determine  this  rise, 
measure  both  the  narrow  and  wide  ends  of  the  cam  strip, 
and  the  difference  between  these  two  dimensions  will  be  the 
lead  of  the  cam. 

To  select  the  forming  cam  for  operating  the  forming  tool, 
measure  the  distance  between  the  largest  and  smallest  diameters 
of  the  work  formed  by  it,  and  divide  the  result  by  2.  In  this 
case,  it  will  be  found  that  the  forming  cam  should  have  a  rise 
of  -32  inch.  All  forming  cams  are  plainly  marked  on  the  end 
with  the  rise  for  which  they  were  laid  out.  It  is  not  always 
possible  to  select  a  forming  cam  which  will  give  the  rise  to 
within  a  few  thousandths  of  an  inch  of  that  required,  but  this 
does  not  make  much  difference,  as  the  longest  single  opera- 
tion governs  the  time  required  to  make  one  piece,  and  all  the 
other  operations  are  completed  in  that  time.  In  this  example, 
as  is  usually  the  case,  the  forming  is  one  of  the  shorter  opera- 
tions and,  therefore,  it  does  not  matter  if  the  forming  tool 


176  SETTING-UP    SCREW   MACHINES 

moves  a  little  farther  than  is  actually  required,  provided  its 
inward  movement  is  arrested  at  the  proper  point. 

To  select  the  cut-off  cam,  measure  the  diameter  of  the  piece 
to  be  cut  off  and  at  the  same  time  make  allowance  for 
the  angle  on  the  point  of  the  cut-off  tool,  so  that  it  will  pass 
the  center  of  the  work.  For  cutting  off  the  cap-screw  shown 
in  Fig.  1 6,  a  |-inch  cut-off  cam,  which  actually  has  a  rise  on 
the  cam  of  j  inch  for  cutting  through  a  bar  ^  inch  in  diam- 
eter, should  be  selected.  The  cut-off  cams  are  all  marked 
on  the  end  to  correspond  with  the  diameter  of  the  piece  to  be 
cut  off. 

Placing  the  Cams  in  Position.  —  In  placing  the  lead  cam  on 
the  drum,  when  the  operations  performed  from  the  main  tool- 
slide  are  of  a  heavy  nature,  a  backing-up  strip  should  be  fitted 
into  the  groove  in  the  drum,  behind  the  lead  cam,  so  as  to 
resist  the  thrust  of  the  cutting  tools.  A  starting  strip  should 
also  be  put  on  just  in  front  of  the  point  where  the  lead  cam 
strip  starts  to  bring  the  tool-slide  up  to  the  work,  and  a  take- 
back  cam  wide  enough  to  draw  the  end-working  tool-slide  back 
sufficiently  to  clear  the  work  when  the  cylinder  is  indexing 
should  next  be  put  in  place.  This  starting  strip  is  adjusted 
even  with  the  starting  or  narrow  end  of  the  lead  cam,  and  is 
used  to  bring  the  tools  up  quickly  to  the  work.  When  the  roller 
is  working  on  the  "  fast-angle  "  cams,  the  camshaft  is  rotated 
at  an  increased  speed,  so  that  all  the  movements  when  the 
tools  are  not  cutting  are  a  great  deal  more  rapid  than  the  cut- 
ting movements.  This  is  done  to  reduce  the  idle  time  and  is 
accomplished  through  the  medium  of  the  clutch  mechanism 
described  in  Chapter  III. 

In  placing  the  cut-off  cam  in  position,  it  should  be  put  on 
the  disk  opposite  the  one  on  which  the  forming  cam  is  held, 
and  the  take-back  cam  is  also  put  on  the  same  disk  and  at- 
tached by  screws.  There  are  two  sets  of  holes  in  the  disk  for 
the  cut-off  cam,  and  the  position  of  this  cam  on  the  disk  de- 
pends upon  whether  the  "  fourth  "  end  tool  position  is  in  use 
or  not.  The  disk  for  the  forming  cam  has  only  one  set  of  holes, 
so  that  it  is  impossible  to  adjust  it. 


ADJUSTMENT  OF  ACME  MACHINE 


177 


Setting  the  Circular  Forming  and  Cutting-off  Tools.  —  The 
circular  forming  tool  A,  Fig.  17,  is  held  to  an  oblong-shaped 
tool-holder  B  by  a  stud  and  nut.  This  holder  is  held  in  the 
slot  in  the  forming  slide  by  a  strap.  For  locating  the  cutting 
edge  of  the  forming  tool  in  the  proper  relation  to  the  work,  a 
tool  setting  gage  C  is  used.  This  is  held  by  the  operator  against 


Fig.  17.   Setting  the  Cutting  Edge  of  a  Circular  Forming  Tool  to 
the  Proper  Height  with  a  Tool-setting  Gage 

the  bottom  face  of  the  forming  tool  holder,  and  the  nut  for 
holding  the  forming  tool  to  the  holder  is  then  tightened.  The 
holder  is  then  placed  in  its  proper  position  in  the  slot  in  the 
tool-slide  and  clamped.  To  bring  the  forming  tool  into  its 
correct  relation  to  the  work,  the  machine  is  cranked  or  turned 
by  hand  until  the  roll  is  just  over  the  starting  angle  on  the 
forming  cam;  then  the  screw  in  the  back  of  the  slide  is  adjusted 
until  the  forming  tool  just  clears  the  work. 


178  SETTING-UP    SCREW    MACHINES 

The  adjusting  screw  on  the  slide  in  which  the  forming  tool 
is  held  should  be  set  to  stop  the  slide  just  as  the  cam  lever 
clears  the  highest  point  of  the  cam.  Usually  it  is  good  prac- 
tice to  put  a  slight  tension  on  this  lever  (by  adjusting 
the  screw  a  little  farther  in  than  necessary),  so  that,  when  the 
extreme  knife  edge  of  the  tool  is  removed,  thus  making  the 
work  larger  in  diameter,  a  slight  outward  turn  of  the  adjusting 
screw  will  bring  the  work  back  to  the  required  diameter. 

The  next  step  is  to  set  the  cut-off  tool.  This  tool,  when 
of  the  blade  type,  is  set  so  that  its  top  cutting  edge  is  on  a 
line  with  the  center  of  the  work.  It  should  also  be  set  in  a 
horizontal  position  relative  to  the  forming  tool,  by  adjust- 
ing the  screw  in  the  slide,  which  is  provided  for  that  purpose. 
After  the  form  and  cut-off  tools  have  been  set  in  approxi- 
mately the  correct  relation  to  each  other,  the  next  step  is  to 
set  the  form  tool  so  that  it  will  turn  the  work  to  the  required 
diameter.  To  do  this,  " crank  the  machine"  or  turn  the 
camshaft  by  applying  a  hand  crank  to  the  worm-shaft,  until 
the  wedge  is  disengaged  from  the  wedge  fingers;  then  push 
the  rod  through  the  chuck  until  its  end  passes  the  outside 
edge  of  the  circular  form  tool.  Continue  cranking  until  the 
rod  is  chucked  and  the  roll  on  the  lever  operating  the  forming 
slide  is  on  the  starting  point  of  the  cam  rise.  The  form  tool 
can  now  be  adjusted  inward,  the  machine  started,  and  a  cut 
taken.  It  is  good  practice  to  adjust  the  form  tool  to  give  the 
required  diameter,  before  going  further.  It  is  necessary  to  set 
the  cut-off  tool  to  remove  the  formed  ends  during  the  adjust- 
ment of  the  forming  tool.  After  one  piece  has  been  cut  off, 
it  can  easily  be  seen  whether  the  cut-off  tool  has  been  set  in 
the  proper  relation  to  the  center  of  the  stock. 

Setting  the  Box-tools.  —  Assuming  that  the  forming  and 
cut-off  tools  have  been  properly  set,  place  the  box-tool  in  the 
"first"  position  tool  spindle.  Then  open  the  chuck  and  feed 
out  the  stock.  When  the  work  is  long  or  of  small  diameter, 
it  is  good  practice,  in  setting  the  box-tool,  to  feed  the  stock 
out  only  a  short  distance  from  the  face  of  the  chuck,  to  pre- 
vent springing  or  bending  of  the  bar  while  adjusting  the  tool. 


ADJUSTMENT  OF  ACME   MACHINE 


179 


In  setting  the  box-tool,  release  the  rollers  and  set  the  front 
turning  tool  to  turn  from  0.005  to  0.007  mcn  smaller  than  the 
proper  diameter,  after  which  adjust  the  rollers  until  they  come 
into  light  contact  with  the  piece  to  be  turned.  Then  by  ad- 
justing the  front  cutting  tool  upward  slightly,  the  tool  and 
rollers  will  come  into  the  proper  relation  with  each  other.  In 


Fig.  18.   Setting  the  "First"  Position  Box-tool  to  turn  to  the  Required  Distance  on 

the  Work 

many  cases,  a  slight  additional  adjustment  of  the  box-tool 
cutter  is  necessary  after  the  machine  has  been  started  and  the 
power  feed  is  used. 

Several  methods  are  in  common  use  for  setting  the  box-tool 
to  turn  to  the  desired  distance.  One  of  these  is  to  crank  the 
machine  until  the  roll  just  starts  on  the  rise  of  the  lead  cam; 
then  to  operate  the  screw  A,  Fig.  18,  in  the  tool  spindle,  until 
the  box-tool  cutter  B  just  touches  the  work  which  it  will  be 


l8o  SETTING-UP   SCREW  MACHINES 

assumed  has  been  fed  out  to  the  required  length.  After  adjust- 
ing in  this  manner,  tighten  the  screw  holding  the  box-tool  in 
position  in  the  tool-holder.  After  the  "first"  position  box-tool 
has  been  set  in  position  in  proper  relation  to  the  work,  the 
power  feed  may  be  thrown  in  to  index  the  cylinder  by  oper- 
ating the  starting  clutch  lever  at  the  front  of  the  machine. 

This  will  bring  the  rod  just  operated  upon  into  the  " second" 
position.  Now  adjust  the  gage  stop  and  set  the  feed  stop 
on  the  lever  operating  the  feeding  mechanism,  so  that  the 
stock  will  be  fed  to  the  length  of  the  piece  to  be  made,  being 
sure  to  ascertain  beforehand  that  the  feed-tube  is  withdrawn 
sufficiently  to  insure  the  end  of  the  rod  coming  in  contact  with 
the  gage  stop.  When  the  stop  has  been  properly  set,  the  stock 
fed  the  proper  distance,  and  the  cam  roll-holders  set  so  as  to 
give  ample  clearance  for  all  tools,  crank  the  machine  until 
the  cam  roll  beneath  the  main  tool-slide  is  in  contact  with 
the  start  of  the  rise  on  the  lead  cam. 

After  having  set  the  " first"  position  box- tool,  again  crank 
the  machine  until  the  forming  tool  and  " first"  position  box- 
tool  have  completed  their  operations  and  another  indexing 
of  the  cylinder  is  about  to  take  place.  After  this  indexing 
has  proceeded  about  halfway,  place  the  "second"  position  box- 
tool  back  far  enough  to  clear  the  stock  during  the  indexing 
operation.  Continue  cranking  until  the  cam  roll  is  in  contact 
with  the  cam,  as  before;  then  adjust  the  "second"  position 
box-tool  so  that  it  will  "pick  up"  or  continue  the  cut  at  the 
position  where  the  "first"  position  box-tool  finished,  and 
at  the  same  time,  set  the  rest  and  front  cutting  tool  to  the 
diameter  formed  by  the  "first"  position  box- tool.  To  bring 
the  box-tool  out  so  as  to  turn  up  the  correct  length,  an  ordi- 
nary scale  C,  as  shown  in  Fig.  18,  is  sometimes  used.  Some 
operators  prefer  the  "scale  method"  of  setting  the  end- working 
tools,  instead  of  working  from  the  end  of  the  bar. 

When  the  screw  is  to  be  pointed,  a  pointing  tool  can  be 
held  in  the  "first"  position  box- tool,  or,  if  the  " fourth"  posi- 
tion tool  spindle  is  not  used,  a  pointing  tool  can  be  used  from 
this  position.  Assuming,  in  this  case,  that  the  pointing  tool 


ADJUSTMENT  OF  ACME  MACHINE          i8l 

is  in  the  "  first "  position  box- tool  and  that  the  gage  stop, 
forming  tool,  box- tools,  etc.,  have  been  properly  set,  release 
the  set-screw  which  holds  the  pointing  tool.  Then  crank  the 
machine  until  the  tool-slide  travels  forward  the  required  dis- 
tance, and  adjust  the  pointing  tool  out  until  it  will  remove 
the  desired  amount  of  metal  from  the  end  of  the  screw. 

Selecting  Change-gears.  —  After  all  the  tools  previously 
mentioned  have  been  set  in  their  proper  positions,  several 
pieces  are  made  from  the  bars,  the  machine  being  operated 
by  power  feed.  Then  change-gears  are  selected  to  give  the 
desired  rate  of  production.  As  a  rule,  in  setting  up  an  Acme 
automatic  screw  machine,  the  gears  which  have  been  decided 
upon  to  give  the  desired  production  are  not  put  on  until  all 
the  tools  have  been  properly  set  and  the  various  parts  of  the 
machine  work  in  the  proper  relation  to  each  other.  Most 
operators  set-up  the  machine  on  a  "slow"  set  of  gears,  and, 
after  the  machine  has  been  set  correctly,  put  on  the  gears 
which  will  give  the  desired  production.  This  change-gear 
mechanism  was  described  in  connection  with  Fig.  4,  Chapter 
III.  For  the  piece  chosen  as  an  example  (see  Fig.  16),  it  was 
decided  that  a  production  of  98.5  pieces  per  hour  would  be 
suitable.  Referring  to  a  table  of  change-gears,  it  will  be  found 
that  the  first  gear  on  the  shaft  should  have  36  teeth;  the  second 
gear  on  the  shaft,  82  teeth;  the  first  gear  on  the  stud,  74  teeth; 
and  the  second  gear  on  the  stud,  28  teeth.  After  these  gears 
have  been  put  in  their  proper  positions,  the  next  step  is  to 
set  the  threading  spindle. 

Setting  the  'Threading  Spindle.  —  On  the  Acme  multiple- 
spindle  automatic  screw  machine,  the  work-spindle  is  held 
stationary  while  a  right-hand  thread  is  being  cut,  and  the  die- 
spindle  carrying  the  threading  tool  is  rotated.  When  backing 
off  the  die  or  tap  from  the  work,  the  threading  spindle  is  held 
stationary  and  the  work-spindle  is  rotated.  The  manner  in 
which  this  is  accomplished  was  explained  in  connection  with 
the  description  of  the  threading  mechanism  in  Chapter  III. 

In  setting  the  tools  for  threading,  before  starting  the  ma- 
chine, see  that  the  clearance  between  the  ratchet  and  pawl 


182  SETTING-UP   SCREW   MACHINES 

extension  is  anywhere  from  yg-  to  -g-  inch,  when  the  pin  block 
on  the  holder  and  the  pin  in  the  spindle  are  placed  end  to  end 
(after  the  pin  has  been  adjusted).  It  is  very  important  that 
this  precaution  be  taken,  as  a  "  hang  up  "  between  these  two 
points  might  occur,  resulting  in  the  stripping  of  the  teeth 
in  the  gears  driving  the  holder,  should  this  adjustment  not  be 
made  properly.  For  this  example,  the  front  face  of  the  die 
should  be  set  almost  in  line  with  the  cutting  tool  held  in  the 
box- tool  in  the  " first"  tool  position,  when  the  die-spindle  is 
as  far  back  as  the  tool-slide  will  let  it  go. 

The  lead  cam  does  not  advance  the  threading  tool  at  the 
required  rate  of  feed,  as  determined  by  the  thread,  but  pro- 
vision is  made  so  that  the  die  follows  the  lead  of  the  thread. 
It  is,  therefore,  unnecessary  to  take  the  lead  cam  into  considera- 
tion, as  far  as  the  feeding  of  the  die-spindle  is  concerned. 
The  die  pins  which  actuate  the  die-holder  for  driving  the 
threading  die  should  be  set  so  as  to  carry  the  die  up  far  enough 
after  the  end  of  the  travel  of  the  lead  cam  has  been  reached, 
before  allowing  the  die  to  rotate  freely.  In  this  case,  the  lead 
cam  only  travels  approximately  one  inch,  while  the  travel  of 
the  die  is  ij  inch,  so  that  it  will  be  necessary  to  set  out  the  die 
pins.  After  all  the  tools  have  been  properly  adjusted  and  are 
working  satisfactorily,  set  the  cam  dogs  which  shift  the  clutch 
to  the  direct  drive,  so  that  they  operate  at  the  proper  time  in 
relation  to  the  cutting  tools  and  the  indexing  of  the  cylinder. 
As  a  general  rule,  the  clutch  should  be  shifted  to  the  direct  drive 
when  the  die  or  tap  is  just  free  from  the  thread  and  the  rolls 
have  cleared  the  cutting-off  and  forming  cams.  The  clutch  again 
shifts  to  the  gear  drive  just  before  the  tools  begin  to  operate. 

Calculating  Speed  of  Work-spindles.  —  The  speed  of  the 
work-spindles  obtainable  by  direct  drive  and  through  the  back 
gearing  may  be  obtained  from  tables,  but  it  might  be  pos- 
sible, in  some  cases,  to  secure  more  satisfactory  speeds  with 
gears  having  a  different  number  of  teeth  than  those  given  in 
the  table.  The  calculations  used  in  obtaining  the  proper  gears 
to  use  for  different  speeds  will  be  explained.  The  work- 
spindles  are  rotated  from  the  main  drive  shaft  through  gear- 


ADJUSTMENT  OF  ACME  MACHINE  183 

ing,  the  gears  on  the  main  shaft  driving  the  spindles  through  a 
friction  gear  that  can  be  disconnected  from  the  spindle  when 
it  is  necessary  to  stop  its  rotation  for  performing  operations 
such  as  threading,  cross-drilling,  milling,  etc.  As  there  are 
only  two  gears  involved  in  this  calculation,  the  method  of 
obtaining  the  speeds  of  the  spindle  is  simple  and  can  be  obtained 
from  the  following  formula  : 

rXN 

K  =  -        —  , 

n 
in  which  R  =  revolutions  per  minute  of  work-spindles; 

r  =  revolutions  per  minute  of  top  or  main  drive  shaft; 
N  =  number  of  teeth  in  gear  on  top  or  main  drive  shaft; 
n  =  number  of  teeth  in  friction  gear. 

For  example,  on  the  No.  54  machine,  R  =  —  -       -  =  373 

45 

revolutions  per  minute,  approximately.  In  the  calculations 
to  follow,  particular  reference  will  be  made  to  the  Nos.  54 
and  55  machines,  as  these  two  sizes  meet  general  commercial 
requirements. 

Calculating  Speeds  of  Threading  and  "  Second  Position  " 
Tool  Spindles.  —  A  notable  feature  of  the  Acme  multiple- 
spindle  automatic  screw  machine  is  that,  for  threading,  the 
work  is  stopped  and  the  die  is  rotated,  but,  in  backing  off, 
the  reverse  is  the  case.  In  order  to  fulfill  these  requirements, 
it  is  necessary  to  gear  up  the  threading  spindle  to  the  main 
drive  or  top  shaft.  Two  speeds  for  each  speed  of  the  top  or 
main  drive  shaft  are  possible  by  shifting  the  gearing,  one  speed 
being  obtained  by  driving  direct  through  the  sliding  gear  on 
the  main  drive  shaft  to  the  gear  on  the  threading  spindle,  and 
the  other  by  driving  through  an  intermediate  and  a  compound 
gear.  The  following  formula  is  used  for  obtaining  the  speed 
of  the  spindle  when  driven  direct  : 


7? 

~r~' 

in  which 

RI  =  revolutions  per  minute  of  threading  spindle  (direct  drive)  ; 
r  =  revolutions  per  minute  of  top  or  main  drive  shaft; 


1  84  SETTING-UP   SCREW  MACHINES 

^Vi  =  number  of  teeth  in  sliding  gear  on  top  or  main  drive  shaft; 

t  =  number  of  teeth  in  gear  on  threading  spindle  (also  called 
direct  gear). 

As  an  example,  assume  that  the  speed  of  the  top  or  main 
drive  shaft  is  480  revolutions  per  minute,  then  : 

480  X  26 
RI  =  -   -  =227  revolutions  per  minute,  approximately. 

55 

The  formula  for  obtaining  the  speed  of  the  threading  spindle, 
when  driven  through  the  intermediate  and  compound  gear, 
is  as  follows  : 

r  X  Ni  X  T 
KZ  =  -  , 
»iX  / 

in  which 
Rz  =  revolutions  per  minute,  of  threading  spindle  (gear-driven)  ; 

r  =  revolutions  per  minute,  of  top  or  main  drive  shaft  ; 
NI  =  number  of  teeth  in  sliding  gear  on  main  drive  shaft  ; 

T  =  number  of  teeth  in  pinion  gear  ; 
n\  =  number  of  teeth  in  back-gear  ; 

/  =  number  of  teeth  in  gear  on  threading  spindle  (also  called 
direct  gear). 

The  "second  position"  tool  spindle  which  can  be  used  for 
threading,  if  necessary,  and  which  in  many  cases  is  used  for 
driving  small  drills  at  their  proper  peripheral  speeds,  is  also 
rotated  from  the  top  or  main  drive  shaft  through  gears.  The 
speed  of  this  spindle  can  be  obtained  by  the  following  formula  : 

rX  N, 
*3=~, 

in  which 
Ra  =  revolutions  per  minute  of  "second  position"  tool  spindle  ; 

r  =  revolutions  per  minute  of  top  or  main  drive  shaft  ; 
Ni  =  number  of  teeth  in  sliding  gear  on  main  drive  shaft  ; 
T\  =  number  of  teeth  in  gear  on  "second  position  "  tool  spindle. 
Assume  that  the  speed  of  the  main  drive  shaft  is  480  revolu- 
tions per  minute,  then  : 
480  X  26 


36 


=  346  revolutions  per  minute,  approximately. 


1 86  SETtlNG-TJP    SCREW   MACHINES 

Main  Camshaft  Computations.  —  The  main  camshaft  on 
the  Acme  automatic  carries  all  the  cams  for  operating  the  vari- 
ous slides,  spindle-stopping  mechanism,  etc.,  and  also  the  fan 
gear  for  indexing  the  cylinder.  As  shown  in  Fig.  19,  which  is 
a  developed  plan  view  of  the  camshaft  with  the  drums  and 
cams  on  it,  it  will  be  seen  that  one  revolution  of  this  camshaft 
completes  one  cycle  of  the  machine;  that  is,  one  revolution 
of  the  camshaft  would  mean  the  completion  of  one  piece,  or 
four  revolutions  the  complete  indexing  of  the  cylinder.  The 
rotation  of  the  camshaft  is  not  connected  directly  with  the 
rotation  of  the  work-spindles,  but  indirectly  the  cams  on  it 
govern  the  rate  of  travel  of  the  tools  on  either  the  top-  or  side- 
working  tool-slides,  and  also  the  end-working  slide.  It  is, 
therefore,  necessary  to  determine  for  each  job  the  relation  be- 
tween the  speed  of  the  spindle  and  the  speed  of  the  camshaft 
in  order  to  determine  the  production  per  hour,  minutes,  or 
seconds. 

The  camshaft  is  driven  from  the  main  drive  pulley  through 
bevel  gearing  and  a  Johnson  clutch.  The  clutch  forms  the 
connection  between  the  direct  drive  and  gear  drive  to  the 
camshaft,  so  that  it  is  possible  to  rotate  the  camshaft  at  a 
much  higher  speed  for  the  idle  movements  than  the  speed  at 
which  it  is  operating  when  the  tools  are  cutting.  The  speed 
of  the  camshaft,  when  driven  direct,  may  be  obtained  from  a 
table,  accompanying  the  machine,  giving  the  number  of  pieces 
produced  per  hour,  as  this  number  will  represent  the  number 
of  revolutions  the  camshaft  makes  in  one  hour.  For  example, 
the  camshaft  on  the  Nos.  54  and  55  machines  has  a  speed  of 
576  revolutions  per  hour.  Dividing  576  by  60,  the  camshaft 
will  be  found  to  make  9.6  revolutions  per  minute  or  0.16  revo- 
lution per  second.  As  there  are  360  degrees  in  a  circle,  and 
as  any  point  on  the  cam  drum  makes  0.16  revolution  per  sec- 
ond, the  number  of  degrees  passed  through  in  this  time  equals 
o.i 6  X  360  =  57.6  degrees,  approximately.  Now,  if  it  takes 
one  second  for  the  camshaft  to  rotate  through  a  space  of  57.6 
degrees,  the  time  required  to  complete  the  idle  movements 
can  easily  be  found,  when  the  number  of  degrees  taken  up  by 


1 88  SETTING-UP    SCREW   MACHINES 

the  idle  or  non-productive  movements  are  obtained.  By  refer- 
ring to  Fig.  20,  in  which  the  various  drums  and  cams  have  been 
laid  out  in  their  respective  positions,  and  at  the  point  in  their 
rotation  at  which  the  machine  is  indexing,  it  will  be  seen  that 
the  non-productive  movements  come  in  between  the  time  that 
the  lead  cam  A  starts  to  operate  and  finishes.  This  applies 
when  the  longest  single  operation  is  performed  by  the  end- 
working  tools  or  from  the  forming  slide.  Where  the  longest 
operation  is  performed  from  the  cutting-off  slide,  the  idle  time 
is  less  because  there  are  thirty  more  degrees  taken  up  on  pro- 
ductive work.  It  is  safe  to  assume  that,  on  75  per  cent  of  the 
jobs  set  up  on  this  machine,  the  longest  operation  is  performed 
from  the  end-working  tool-slide;  hence,  the  calculations  can 
be  based  on  the  number  of  degrees  of  drum  surface  between 
the  starting  and  finishing  points  of  the  cam.  This  is  found  to 
be  360  —  220  =  140  degrees.  When  the  longest  single  opera- 
tion is  performed  from  the  cut-off  tool-slide,  the  idle  move- 
ments occupy  no  degrees  of  the  drum  circumference. 

Time  required  for  Idle  Movements  of  Machine.  —  The 
idle  movements  of  the  machine  are  those  required  for  advanc- 
ing and  withdrawing  the  tools  to  and  from  the  work  and 
indexing  the  cylinder.  The  stock  is  fed  out  and  the  chuck 
closed  while  the  cylinder  is  indexing  on  the  smaller  machines 
and  in  the  "first  position"  on  the  larger  machines,  but,  in  all 
cases,  as  can  be  seen  from  a  study  of  Fig.  20,  the  idle  move- 
ments more  than  compensate  for  the  time  required  to  feed 
out  the  stock.  The  three  main  idle  or  non-productive  move- 
ments of  the  machine  should  be  considered  in  calculating  the 
actual  time  required  for  producing  a  given  part.  These 
movements  are  all  confined  to  the  space  between  B  and  C  on 
the  circumference  of  the  cam  drum.  As  all  the  non-productive 
movements  take  place  while  the  camshaft  is  being  driven  at 
its  highest  speed  —  direct  through  the  clutch  and  not  through 
the  change  gearing  —  it  is  necessary  to  determine  what  part 
of  the  cam  circumference  these  movements  occupy  and  also 
the  speed  at  which  the  drum  is  being  rotated  when  driven 
direct. 


ADJUSTMENT  OF  DAVENPORT  MACHINE  189 

As  previously  determined,  the  idle  movements  or  the  space 
on  the  cam  circumference  from  B  to  C  equals  140  degrees,  and, 
on  the  Nos.  54  and  55  machines,  the  camshaft,  when  driven 
direct,  is  rotated  at  a  speed  of  0.16  revolution  per  second. 
If  it  takes  one  second  for  the  camshaft  to  rotate  through 
a  space  of  57.6  degrees,  it  will  require  140  -£•  57.6,  or  2.43 
seconds,  approximately,  for  the  idle  movements.  This  time, 
if  added  to  the  time  required  for  the  longest  single  operation, 
will  give  the  actual  time  required  to  complete  one  piece. 

Setting-up  the  Davenport  Automatic.  —  The  method  of 
setting-up  and  adjusting  the  Davenport  multiple-spindle  au- 
tomatic screw  machine  illustrated  in  Fig.  10,  Chapter  III, 
will  be  explained  by  considering  the  method  of  procedure  for 
making  a  J-inch  machine  screw.  The  successive  order  of  the 
operations  and  the  tools  to  be  used  should  first  be  determined. 
In  this  case,  the  order  of  operations  is  indicated  by  the  dia- 
grams A  to  E,  inclusive  (Fig.  21)  and  the  finished  product  is 
shown  at  F.  The  principal  operation  is  that  of  rough-turning 
the  body  of  the  screw,  and,  in  order  to  reduce  the  time  per 
piece,  two  box- tools  are  used  as  indicated  at  A  and  B.  The 
tool  in  the  first  spindle  turns  one-half  of  the  required  length, 
and  then  the  remaining  half  is  rough- turned  by  the  other 
box-tool  in  the  second  spindle.  When  the  first  box- tool  is  at 
work,  a  forming  tool  on  the  cross-slide  cuts  away  the  metal 
on  both  sides  of  the  screw-head,  as  the  illustration  indicates. 
The  finishing  cut  is  taken  by  a  single  box- tool  in  the  third 
spindle  (diagram  C) ;  this  tool  is  given  twice  the  feed  of  the 
roughing  box-tools,  so  that  the  finishing  cut  will  be  completed 
in  the  same  length  of  time  required  for  the  two  roughing  cuts. 
A  die  is  next  used  to  cut  the  thread,  as  indicated  at  Z>,  and 
then  the  finished  screw  is  severed  from  the  bar  of  stock  by 
the  cutting-off  tool,  as  shown  at  E.  The  end  or  point  of  the 
stock  is  also  rounded  by  the  cutting-off  tool,  preparatory  to 
making  the  next  successive  screw. 

Speed  for  Work-spindles.  —  The  machine  is  geared  so  that 
the  work-spindles  will  revolve  at  whatever  speed  is  considered 
essential  to  economical  production.  For  ordinary  screw  stock, 


SETTING-UP   SCREW  MACHINES 


a  surface  speed  of  about  100  feet  per  minute  is  considered  a 
fair  average  for  this  machine.  The  material,  in  this  case,  is 
-j^-inch  hexagonal  steel  (a  special  size  for  a  J-inch  screw),  so 
that  the  surface  speed  may  be  based  upon  a  diameter  of  y76 


Machinery 


Fig.  21.   Examples  of  Work  done  on  Davenport  Five-spindle  Automatic 

inch.  By  referring  to  the  table  of  spindle  speeds  and  corre- 
sponding change-gears  to  use,  it  will  be  found  that  the  spindle 
speed  should  be  840  revolutions  per  minute,  which  speed  is 
obtained  by  equipping  the  machine  with  a  driving  gear  having 
28  teeth  and  a  driven  gear  having  36  teeth.  This  speed  of  840 


ADJUSTMENT   OF   DAVENPORT   MACHINE  191 

revolutions  per  minute  will  give  a  surface  speed  of  approxi- 
mately 100  feet  per  minute. 

Number  of  Revolutions  for  Each  Operation.  —  The  next 
step  is  to  determine  the  number  of  revolutions  the  spindles 
make  for  each  of  the  operations.  The  number  of  revolutions 
which  the  spindles  make  for  any  given  operation  depends 
upon  the  feed  of  the  tool  per  revolution  and  the  length  of  the 
part  to  be  turned ;  therefore,  it  is  necessary  to  first  decide  what 
feeds  are  to  be  used.  For  rough-turning,  the  feed  usually  varies 
from  0.004  to  o.oio  inch  per  revolution  of  the  spindles  and,  in 
this  case,  it  will  be  assumed  that  a  feed  of  0.0075  mcn  *s  to  be 
used  for  roughing  and  twice  that  amount,  or  0.015  mch)  for  the 
finishing  cut,  so  that  the  box-tool  which  takes  this  finishing 
cut  will  traverse  i-jf  inch  or  over  the  entire  body  of  the  screw, 
while  each  of  the  roughing  tools  is  feeding  f  f  inch  or  one-half 
the  length  of  the  screw  body.  By  dividing  the  length  of  the 
turned  surface  by  the  feed  per  revolution,  it  will  be 
found  that  approximately  121  revolutions  are  necessary, 
(1.8 1 2  -f-  0.015)  =  I2I>  nearly.  Adding  two  revolutions  to 
allow  for  a  little  clearance,  for  indexing,  between  the  ends  of 
the  tools  and  the  stock,  gives  a  total  of  123  revolutions  of  the 
spindles. 

After  having  determined  the  number  of  revolutions  of  the 
spindles  for  the  longest  operation,  the  machine  is  equipped 
with  change-gears  at  U,  Fig.  13,  Chapter  III,  as  indicated  by 
a  table  accompanying  the  machine.  Under  the  heading  "  Revo- 
lutions per  Minute  of  Spindles"  and  in  the  column  headed 
"840"  (which  represents  the  selected  speed  of  spindles  and 
revolutions  per  minute)  will  be  found  the  figure  123  represent- 
ing the  number  of  spindle  revolutions  required  for  the  forward 
feeding  movement  of  the  tools.  Opposite  123,  the  necessary 
change-gears  are  listed  and  also  the  rate  of  production.  These 
gears  transmit  motion  to  the  camshafts.  In  this  case,  the  gear 
on  the  driving  shaft  has  20  teeth  and  the  gear  on  the  driven 
shaft,  44  teeth.  The  time  in  seconds  required  to  make  one 
piece,  which  includes  the  time  for  withdrawing  the  tools  and 
indexing,  is  1 2  seconds  per  piece. 


192  SETTING-UP   SCREW   MACHINES 

Selection  of  Cams.  —  Seventeen  cams  are  furnished  with 
the  Davenport  multiple-spindle  automatic  machine.  Six  of 
these  cams  are  intended  for  turning  operations,  two  for  point- 
ing the  ends  of  the  stock,  four  for  threading  operations,  and 
five  for  forming  and  cutting-off  operations.  The  rise  or  throw 
of  the  cams  varies ;  for  instance,  among  the  cams  used  for 
turning,  there  is  one  having  a  rise  of  ^  inch  (used  for  center- 
ing and  facing  operations) ;  another  having  a  rise  of  ^  inch ;  two 
others,  a  i-inch  rise,  and  two  additional  cams,  a  2 -inch  rise. 
If  the  travel  required  for  the  tool  differs  from  the  rise  or  throw 
of  the  cam,  the  motion  of  the  tool  is  varied  by  changing  the 
position  of  the  link  connecting  the  cam  lever  with  the  tool 
spindle,  as  previously  explained  in  Chaper  III.  When  setting- 
up  a  machine,  cams  are  selected  for  each  operation  which  are 
nearest  to  the  required  size  as  to  rise,  but  which  have  a  rise, 
in  every  case,  that  is  equal  to  or  greater  than  the  travel  re- 
quired for  the  tool.  When  these  cams  have  been  placed  in 
position,  the  adjustable  blocks  at  the  upper  ends  of  the  cam 
levers  are  set  so  that  each  tool  will  travel  the  exact  distance 
required  on  the  work.  After  making  these  adjustments,  the 
feed  for  most  of  the  tools  will  be  finer  than  those  first  selected, 
but,  as  the  time  for  making  a  screw  is  governed  by  the  longest 
operation,  an  increase  in  the  number  of  revolutions  that  the 
spindles  make  during  some  of  the  shorter  cuts  simply  means 
that  these  tools  will,  in  most  cases,  leave  a  finer  finish  and  will 
last  longer,  owing  to  the  feed  reduction. 

Adjustments  for  Threading  Operation.  —  The  rise  of  the 
cam  to  use  for  operating  the  threading  die  spindle  and  the 
position  of  the  link-block  on  the  cam  lever  are  shown  by  a 
table.  This  table  shows  what  the  rise  of  the  cam  should  be 
for  a  given  number  of  threads  per  inch,  and  also  the  position 
of  the  link-block  on  the  cam  lever.  The  figures  denoting  the 
cam  rise  and  the  graduation  on  the  cam  lever  are  listed  under 
the  required  number  of  threads  per  inch  to  be  cut,  and  oppo- 
site the  number  of  turns  which  the  work-spindle  makes  while 
a  part  is  being  machined.  When  the  cam-lever  block  is  cor- 
rectly set,  the  die-holder  will  follow  up  the  thread,  although 


ADJUSTMENT  OF  DAVENPORT  MACHINE  193 

the  clutch  pins  of  the  die-holder  permit  a  slight  axial  move- 
ment, so  that  the  die  is  free  to  follow  the  lead  of  the  thread. 
When  the  die  is  running  off  of  the  thread,  the  spindle  carrying 
the  die-holder  is  moved  in  the  opposite  direction  by  the  cam, 
and  the  die-holder  is  provided  with  a  ratchet  which  catches 
on  the  first  revolution  after  the  threading  clutch  is  shifted  from 
the  low-speed  gear  to  the  high-speed  gear.  No  adjustment  of 
the  cam  which  controls  the  clutch  of  the  threading  spindle 
is  required  for  any  pitch,  as  the  clutch  is  always  shifted  just 
after  the  die-cam  has  reached  the  highest  point. 

Record  of  Operations.  —  It  is  good  practice,  preparatory 
to  setting-up  the  machine  for  producing  a  new  part,  to  lay 
out  the  operations  as  shown  in  Fig.  21,  and  then  record  the 
order  of  the  operations,  the  tools  used,  etc.,  so  that  the  machine 
can  readily  be  adjusted  or  set-up  for  reproducing  the  same 
part.  Such  data  are  also  useful  for  comparative  purposes, 
when  estimating  on  other  work  which  is  similar  in  size  and 
shape.  The  data  recorded  on  page  194  apply  to  the  operations 
shown  by  the  diagrams  A  to  E,  Fig.  21.  As  will  be  seen,  a 
standard  box-tool  set  to  turn  to  0.265  inches  in  diameter  is 
used  for  the  first  roughing  cut.  This  tool  is  actuated  by  a 
cam  having  a  rise  of  one  inch.  As  the  tool  is  to  turn  one-half 
of  the  length  of  the  screw  body,  or  f  f  inch,  the  block  of  the 
cam  lever  is  set  to  the  0.9  division,  thus  reducing  the  amount 
that  the  tool  travels.  For  the  forming  operation,  which  is 
performed  by  a  tool  in  the  cross-slide  at  the  same  spindle  posi- 
tion, a  -fz-inch  cam  is  used,  and,  as  the  feeding  movement  of  the 
tool  is  only  •£%  inch,  the  cam-lever  block  is  set  at  the  0.8  di- 
vision. In  a  similar  manner,  the  data  for  the  other  turning 
tools  is  recorded.  Ordinarily,  it  is  easier  to  make  all  the  neces- 
sary calculations  beforehand  and  then  adjust  the  machine 
accordingly,  than  to  attempt  to  set  the  machine  as  each  cal- 
culation is  made. 

Turning  a  Trial  Piece.  —  After  the  machine  has  been 
equipped  with  the  necessary  cams,  chucks,  etc.,  it  is  cus- 
tomary to  put  a  single  bar  of  stock  in  one  spindle  and  adjust 
each  tool,  as  the  head  is  indexed  to  the  different  positions, 


SETTING-UP   SCREW  MACHINES 


so  that  all  the  tools  have  the  correct  movement  in  a  length- 
wise direction.  These  adjustments  are  made  by  means  of  the 
turnbuckles  G  which  are  shown  in  Fig.  n,  Chapter  III.  After 
all  of  the  tools  in  the  end-working  spindles,  as  well  as  those  on 
the  cross-slides  and  swinging  arms,  in  case  it  is  necessary  to 
use  the  latter,  are  adjusted  to  approximately  the  correct  posi- 
tion, the  five  bars  of  stock  should  be  inserted  in  the  machine 
spindles  and  the  final  adjustments  made. 

Order  of  Operations  and  General  Data  for  Producing  Screw  shown  at  F, 

Fig.  21 


Operations 

Tools  Used 

Size  of 
Cams, 
Inch 

Feed  of 
Tool, 
Inch 

Feed  per 
Revolution 

Effective 
Revolutions 

Location 
of  Block 

Turn  to  0.265 

Standard  Box 

I 

H 

0.0075 

I23 

0.9 

Form  to  0.265 

Forming 

* 

ft 

O.OO08 

123 

0.8 

Turn  to  0.268 

Standard  Box 

I 

II 

0.0075 

123 

0.9 

Turn  to  0.250 

Standard  Box 

2 

ill 

0.015 

123 

0.9 

Thread 

Die  and 
Holder 

i| 

it 

— 

123 

0.86 

Cut-off 

Cut-off 

A 

0.174 

0.0015 

I23 

0.8 

Surface  speed,  100  feet  per  minute;    spindle  speed,  840  R.P.M.;   gears,  28-36;   seconds  per 
piece,  12;  feed  gears,  20-44. 

Regulation  of  Stock-feeding  Movement.  —  The  stock  is 
always  fed  against  a  stop  which  forms  a  part  of  the  box-tool 
or  other  tool  in  the  first  spindle  or  " position  A"  and  the 
length  to  which  the  stock  is  fed  out  of  the  chuck  is  regulated 
by  a  screw  at  the  rear  end  of  that  tool  spindle.  This  screw 
is  tapped  into  the  spindle  carrier,  and  the  head  of  the  screw 
engages  a  latch  on  the  tool  spindle  and  prevents  the  spindle 
from  moving  back  farther  than  is  necessary  for  the  length 
of  stock  required.  When  it  is  desired  to  draw  the  tool  spindle 
farther  back,  this  latch  attached  to  the  rear  end  of  the  spindle 
is  lifted.  The  turnbuckle  for  this  spindle  is  adjusted  for  the 
position  of  the  cutting  tool  independently  of  the  stop-screw 


ADJUSTMENT  OF  DAVENPORT  MACHINE  195 

just  referred  to.  The  nut  at  the  extreme  left-hand  end  of  the 
crankshaft  should  be  adjusted  to  feed  the  stock  about  |  inch 
farther  than  is  represented  by  the  length  of  the  finished  piece, 
to  insure  a  firm  contact  of  the  stock  against  the  stop. 

Use  of  Thread  Spindle  for  Other  Operations.  —  When  the 
work  does  not  require  a  threading  operation  and  it  is  desired 
to  use  some  other  kind  of  tool  in  the  threading  spindle,  one  of 
the  change-gears  which  rotates  the  threading-spindle  driving 
shaft  can  be  removed,  and  a  square-head  set-screw  engaged 
with  a  tooth  space  of  the  intermediate  gear  through  which 
the  threading  clutch  gears  are  rotated.  By  locking  the  inter- 
mediate gear  in  this  way,  the  clutch  gear  teeth  will  act  as  keys 
and  prevent  the  threading  spindle  from  turning  around,  but 
permit  it  to  slide  freely,  so  that  it  can  be  used  for  holding  an 
end-working  tool  the  same  as  any  of  the  other  spindles. 

Independent  Feeding  Movement.  —  An  example  of  work 
done  on  the  Davenport  multiple-spindle  automatic  machine 
is  shown  by  the  series  of  diagrams  G  to  K,  inclusive,  in  Fig.  21, 
which  illustrate  the  advantages  of  a  separate  feed  for  each  of 
the  turret  and  cross-slide  tools.  The  operations  for  the  first 
spindle  position  are  performed  by  a  forming  tool  on  the  cross- 
slide  and  an  end-facing  tool.  The  tool-slide  advances  o.oio 
inch  for  facing  the  end  accurately  and  smoothly,  and  the  form- 
ing tool  rough- turns  the  work,  leaving  about  o.oio  inch  on  the 
diameter  and  width  of  the  groove  for  finishing.  The  next  suc- 
cessive operation  is  indicated  at  H.  The  tool-slide  advances 
0.040  inch  for  centering  the  work,  and  it  has  a  long  dwell  at 
the  end  of  ^  the  feeding  movement,  thus  insuring  an  accurate 
center.  A  forming  tool  also  turns  the  part  to  the  required 
diameter  and  the  groove  to  the  finished  width.  A  stop-screw 
on  the  toolpost  comes  against  a  compensating  stop  for  each 
spindle,  to  insure  uniformity  of  diameters.  At  the  next  spindle 
position  indicated  at  /,  the  tool-slide  advances  jfa  incn  f°r 
drilling  the  hole.  This  drill  is  revolved  rapidly  by  a  drilling 
attachment  driven  by  a  round  belt  from  the  countershaft,  so 
that  the  actual  cutting  speed  is  the  speed  of  the  work  plus  the 
speed  of  the  drill  spindle.  The  tool-slide  next  advances  -jV 


196  SETTING-UP  SCREW  MACHINES 

inch  for  finish-turning  a  shoulder  as  at  / ;  this  shoulder  must 
be  very  accurate  and  it  was  roughed  out  by  the  cutting-off 
tool  at  the  time  that  it  severed  the  previously  finished  part. 
For  the  final  operation  shown  at  K,  the  tool-slide  advances 
f  inch  for  reaming  the  hole.  As  but  little  metal  is  removed,  the 
feed  is  rapid.  When  the  operation  is  completed,  the  reamer  is 
quickly  withdrawn  and  the  cutting-off  tool,  which  has  been  at 
work  in  the  meantime,  severs  the  piece  which  drops  from  the 
bar. 


CHAPTER   VI 
ATTACHMENTS  FOR  AUTOMATIC   SCREW  MACHINES 

THE  variety  of  work  for  which  an  automatic  screw  machine 
is  applicable  may  be  greatly  increased  by  the  addition  of 
auxiliary  attachments.  Some  of  these  attachments  are  de- 
signed to  do  work  which  could  not  be  done  with  the  ordinary 
tool  equipment,  thus  enabling  the  machine  to  complete  a  series 
of  operations  and  produce  finished  parts  without  a  second 
operation  upon  another  machine.  Other  attachments  are 
designed  for  automatically  feeding  separate  parts,  such  as 
castings  or  forgings,  to  the  machine  or  for  transferring  pieces 
requiring  a  second  operation  to  an  attachment  operating  in 
conjunction  with  the  machine.  While  screw  machines  made 
by  different  manufacturers  are  often  equipped  with  attach- 
ments for  doing  the  same  class  of  work,  these  attachments 
usually  vary  considerably  in  their  design,  as  they  are  con- 
structed for  application  to  a  certain  type  of  machine.  Some 
of  the  more  common  attachments  will  be  described. 

Screw  Slotting  Attachments.  —  The  screw  slotting  attach- 
ment is  used  for  milling  a  screw-driver  slot  across  the  head  of 
a  screw,  after  the  latter  has  been  turned  and  threaded  by  the 
regular  mechanism  of  the  machine.  One  of  these  attachments 
is  shown  applied  to  a  Brown  &  Sharpe  machine  in  Fig.  i. 
This  attachment  is  designed  to  take  screws  as  they  are  cut 
off  by  the  machine  and  to  slot  them  automatically,  thus  elimi- 
nating a  second  operation  in  another  machine  and  completing 
the  screw  in  practically  the  same  time  that  would  be  required 
to  finish  it  without  the  slotting  operation.  The  saw  which 
does  the  slotting  is  mounted  on  a  slide  and  is  driven  by  a  round 
belt  from  the  overhead  works.  The  arm  F  which  transfers 
the  screw  from  the  machine  spindle  to  the  saw  is  actuated  by 
a  cam  K  through  a  lever  connecting  with  rockshaft  C.  The 

197 


i98 


ATTACHMENTS 


screws  are  held  in  a  bushing  carried  in  a  " floating  holder" 
located  at  the  end  of  the  transfer  arm  F.  This  transfer  arm  is 
swung  down  so  that  the  bushing  is  in  line  with  the  work  in 
the  main  spindle,  and  the  bushing  engages  the  work  before  it 
is  severed  from  the  bar  of  stock.  After  the  screw  is  cut  off, 


FACE  OF  CHUCK 


Fig.  1.   Front  Elevation  and  Plan  of  Screw-slotting  Attachment  for  Brown 
&  Sharpe  Screw  Machine 

the  arm  swings  up  to  the  position  shown  in  the  illustration. 
The  rockshaft  C  is  then  fed  longitudinally  towards  the  slotting 
saw  by  means  of  the  advancing  cam  /  which  imparts  motion 
through  lever  E.  When  the  slot  in  the  screw-head  has  been 
cut  and  arm  F  drops  back,  the  screw  is  removed  from  the  bush- 
ing by  the  ejector  K\,  which  is  simply  a  piece  of  sheet  steel 
fastened  to  the  attachment.  The  transfer  arm  F  is  accurately 


SLOTTING  ATTACHMENTS  199 

located  with  reference  to  the  spindle  by  set-screw  E\,  which 
engages  block  F\,  whereas  the  set-screw  G\  and  block  HI 
control  the  position  of  the  arm  with  reference  to  the  saw. 

Slotting  and  Slabbing  Attachment.  —  The  attachment 
shown  in  position  on  the  Cleveland  automatic  screw  machine 
in  Fig.  2  is  used  for  slotting  the  heads  of  screws,  slabbing 
operations,  and  similar  work.  The  operation  is  done  while 
the  turret  tool  is  working,  so  that  no  time  is  lost.  The  opera- 
tion on  a  screw  is  as  follows :  After  the  part  has  been  finished, 
and  is  ready  to  be  cut  off,  the  turret  advances  carrying  the 


Fig.  2.   Slotting  and  Slabbing  Attachment  on  Cleveland  Automatic 

screw-slotting  conveyor  A  which  takes  hold  of  the  screw  as 
it  is  severed  from  the  bar.  The  stock  is  then  fed  forward  and 
the  turret  tools  begin  on  the  next  piece ;  at  the  same  time,  the 
conveyor  A,  carrying  the  screw  that  has  just  been  cut  off,  brings 
the  head  into  contact  with  the  slotting  saw  B.  By  the  time 
the  turret  tool  has  finished  its  cut,  the  saw  has  also  completed 
its  operation.  The  finished  part  is  ejected  from  the  conveyor 
by  means  of  a  pin  C,  upon  the  backward  stroke  of  the  turret. 
The  slotting  arm  D  carrying  the  saw  B  is  a  slight  distance 
back  from  the  face  of  the  chuck  hood,  so  that  it  clears  all  the 
turret  tools,  except  when  the  conveyor  A,  carrying  the  screw, 
comes  into  line  with  it. 


200 


ATTACHMENTS 


The  saw  spindle  is  driven  by  a  belt  from  the  countershaft. 
The  drum  which  carries  the  chuck  opening  and  closing  cams 
has,  in  addition,  another  cam  which  operates  the  slotting 
arm  D.  This  cam  moves  the  saw  toward  the  turret  when  the 
conveyor  A,  held  in  the  turret,  advances  with  the  part  to  be 
slotted.  The  slotting  arm  is  returned  to  its  original  or  neutral 
position  by  the  coil  spring  shown,  after  the  roll  on  arm  D 
comes  out  of  contact  with  the  operating  cam. 

To  fit  up  this  attachment  for  slabbing  operations,  two  slab- 
bing cutters  are  mounted  on  the  saw  spindle  in  the  same 


Fig.  3.  Index  Drilling  Attachment  on  a  Brown  &  Sharpe  Automatic 
Screw  Machine 

manner  as  the  slotting  saw  B,  and  the  same  movement  takes 
place  as  in  slotting.  It  is  also  possible  by  means  of  a  special 
slotting  arm  D  to  cut  a  groove  or  slot  of  any  shape  or  depth 
lengthwise  of  a  piece  by  raising  the  center  of  the  saw  spindle, 
so  that  the  work  will  pass  under  the  milling  cutter  or  saw. 

Index  Drilling  Attachment.  —  The  Brown  &  Sharpe  index 
drilling  attachment  shown  in  Fig.  3  is  designed  to  drill  radial 
holes  in  such  work  as  binding  posts,  capstan  screws,  studs, 
bushings,  and  similar  pieces,  which  are  made  in  the  automatic 
screw  machines.  An  adjustable  swinging  arm  takes  the  pieces 
as  they  are  severed  from  the  bar  and  transfers  them  to  the 
spindle  of  the  drilling  attachment  where  they  are  securely  held 


DRILLING  ATTACHMENTS  2OI 

in  a  spring  chuck  for  drilling.  The  movements  of  the  arm  and 
mechanism  that  control  the  indexing,  the  operation  of  the  spring 
chuck,  and  the  movement  of  the  drill  are  all  governed  by  cams 
located  on  an  auxiliary  camshaft.  The  chain  and  sprocket 
drive  for  rotating  this  camshaft  is  shown  encased  at  the  left 
of  the  illustration.  The  drill  spindle  B  is  driven  by  a  small 
round  belt  from  the  overhead  works,  which  operates  around 
the  idler  pulleys  M.  The  drill  spindle  is  operated  by  cam  C, 
through  lever  D.  The  motion  for  indexing  the  work-spindle 
of  the  attachment  is  obtained  from  cam  F.  This  indexing 


Fig.  4.   Cross-drilling   Attachment  held   on   Cut-off  Tool-slide  of 
Acme  Multiple-spindle  Automatic 

movement  makes  it  possible  to  drill  several  accurately-spaced 
holes  through  the  head  of  a  screw  or  other  part.  One  piece  is 
drilled  by  the  attachment  while  another  is  being  made  by  the 
regular  mechanism  of  the  machine. 

Cross-drilling  Attachment.  —  When  only  a  single  hole  is 
to  be  drilled  cross-wise  through  the  work,  what  is  known  as  a 
cross-drilling  attachment  may  be  used.  This  is  simpler  in  con- 
struction than  the  index  drilling  attachment  (shown  in  Fig.  3) 
and  is  mounted  on  the  cross-slide  when  applied  to  a  Brown 
&  Sharpe  machine.  The  spindle  is  driven  by  a  small  belt  from 
the  overhead  works,  and  the  feeding  movement  for  the  drill 


2O2 


ATTACHMENTS 


is  derived  from  the  cross-slide  itself.  Before  cross-drilling,  it 
is  necessary  to  stop  the  spindle  and  hold  it  rigidly.  On  Brown  & 
Sharpe  machines,  a  spindle  brake  is  used. 

One  of  the  standard  cross-drilling  attachments  used  on  the 
Acme  multiple-spindle  machine  is  shown  in  Fig.  4.  This  con- 
sists of  a  cast-iron  frame  A  which  is  bolted  to  the  top  face  of 
the  cut-off  tool-slide  and  works  in  the  third  position,  where 
the  work-spindle  can  be  stopped.  The  cross-drilling  and  thread- 
ing operations  can  usually  be  performed  at  the  same  time. 
The  drive  for  this  attachment  is  by  a  flat  belt  from  a  special 


Fig.  5.   Acme  Cross-drilling  Attachment  with  Accelerating  Movement 

overhead  countershaft  running  on  the  pulley  B,  which  is 
fastened  to  the  spindle  C  that  carries  the  drill.  This  attach- 
ment, by  a  slight  modification  in  its  construction,  can  be  driven 
by  gears  and  a  universal- joint  shaft  from  the  main  tool-slide. 

Cross-drilling  Attachment  with  Accelerating  Movement.  — 
Another  Acme  cross-drilling  attachment,  but  one  having  an 
accelerating  movement  for  increasing  the  travel  of  the  drill, 
is  shown  in  Fig.  5.  The  attachment  A  is  similar  in  construc- 
tion to  that  shown  in  Fig.  4,  except  that  it  is  mounted  on  two 
slides  B  and  C.  Slide  C  is  fastened  to  the  top  face  of  the  cut-off 
tool-slide,  and  slide  B  fits  over  the  former  and  is  furnished 
with  a  gib  to  provide  for  adjustment.  This  enables  the  drilling 


DRILLING  ATTACHMENTS 


203 


attachment  to  be  moved  longitudinally  along  the  base,  facili- 
tating adjustments  for  the  drilling  of  holes  at  different  distances 
from  the  face  of  the  chuck.  Attachment  A  is  operated  by  a 
lever  D  which  is  fulcrumed  to  the  lower  slide  C. 

A  block  E  provided  with  hardened  adjustable  stops  F  is 
fastened  to  the  base  in  which  the  cut-off  tool-slide  works. 
This  block,  by  means  of  its  adjustable  points,  stops  the  lower 


Machinery 


Fig.  6.   Cross-drilling  Attachment  with  Opposite  Spindles 

portion  of  lever  D,  so  that,  instead  of  following  the  movement 
of  the  cut-off  tool-slide  when  it  is  fed  in,  it  transmits  a  move- 
ment to  the  lower  arm  of  the  lever  and  thus  accelerates  the 
travel  of  the  drill-holder.  The  ratio  between  the  arms  of 
lever  D  is  if  to  i,  thus  making  it  possible  to  drill  a  hole  clear 
through  a  piece.  The  regular  travel  of  the  cross-slide  is  only 
equal  to  a  little  over  one-half  the  diameter  of  the  bar,  so  that, 
when  it  is  necessary  to  drill  a  hole  entirely  through  the  work, 


204 


ATTACHMENTS 


this  attachment  with  accelerated  movements  can  be  used  to 
very  good  advantage. 

Cross-drilling  Attachment  with  Opposite  Spindles.  —  The 
Acme  cross-drilling  attachment  shown  in  Fig.  6  is  provided 
with  opposite  spindles  and  is  adapted  for  drilling  cross  holes, 
and,  in  addition,  counterboring  or  countersinking  from  both 
sides.  It  can  also  be  used  for  drilling  parallel  holes  of  the 
same  or  different  diameters  at  a  given  distance  from  each 
other  and  from  the  face  of  the  chuck.  The  holes  can  either 
be  drilled  entirely  through  the  work  or  to  any  distance  desired. 
When  necessary,  the  attachment  can  be  provided  with  an 


Fig.  7.  Brown  &  Sharpe  Automatic  Screw  Machine  equipped  with 
Turret  Drilling  Attachment 

accelerating  device  for  increasing  its  travel.  The  second 
or  auxiliary  spindle  of  this  attachment  is  driven  by  spur  or 
bevel  gears  from  the  regular  drill  spindle.  When  driven  by 
spur  gears,  the  drive  is  through  gear  A,  shaft  B,  and  gears  C 
and  D.  Gear  D  is  keyed  to  the  spindle  in  which  the  counter- 
sink E  (or  drill)  is  held.  The  bracket  F  carrying  the  auxiliary 
mechanism  is  bolted  to  the  front  side  of  the  regular  attach- 
ment used  for  cross-drilling. 

In  operation,  as  the  cylinder  indexes,  the  stock  comes 
between  the  spindles  of  the  attachment,  and  the  machine  is 
so  cammed  that  the  cut-off  tool-slide  feeds  forward,  drills  the 
first  hole,  and  then  pulls  back  far  enough  to  bring  the  drill 


BURRING  ATTACHMENT 


205 


held  in  the  opposite  spindle  into  contact  with  the  work.  The 
slide  then  feeds  forward  again  to  an  intermediate  position, 
before  the  next  indexing  operation. 

Turret  Drilling  Attachment.  —  The  turret  drilling  attach- 
ment shown  applied  to  a  Brown  &  Sharpe  machine  in  Fig.  7 
is  used  to  increase  the  speed  of  a  drill  relative  to  the  work, 
without  running  the  work-spindle  faster.  This  is  accomplished 
by  rotating  the  drill  in  the  opposite  direction  to  the  stock. 
This  attachment  is  often  used  when  making  small  studs  and 


Fig.  8.   Rear  View  of  the  Burring  Attachment  applied  to  Brown  & 
Sharpe  Automatic  Screw  Machine 

a  variety  of  work  requiring  the  use  of  one  or  more  small  drills 
which  must  be  run  at  a  much  higher  speed  than  is  required 
for  any  other  tool,  in  order  to  obtain  an  economical  cutting 
speed.  The  attachment  is  driven  from  the  overhead  works 
by  a  belt  C  which  rotates  a  spindle  located  at  right  angles  to 
the  spindle  of  the  machine.  This  spindle,  in  turn,  drives  the 
drill  spindles  by  means  of  bevel  gears  G.  The  illustration 
shows  the  turret  equipped  with  two  drill  spindles  A  and  B. 
The  number  may  be  varied  to  suit  the  work. 

Burring  Attachment.  —  The  burring  attachment  shown  in 
Fig.  8  applied  to  a  Brown  &  Sharpe  machine  carries  a  single 
tool  for  removing  burrs  or  for  performing  light  operations,  such 


2o6 


ATTACHMENTS 


as  drilling,  counterboring,  or  facing  on  the  cut-off  ends  of 
pieces  before  they  leave  the  screw  machine.  The  attach- 
ment has  a  work-spindle  C  which  is  driven  from  the  overhead 
works  by  a  small  belt.  The  cutting  tool  is  held  in  this  spindle. 
A  chuck  encased  at  M  attached  to  a  swinging  arm  picks  up 
the  piece  of  work  as  it  is  severed  from  the  bar  and  conveys  it 
first  to  a  device  that  clamps  it  securely  in  the  chuck  and  then 
to  the  tool  in  the  spindle  of  the  attachment.  The  movements 
of  the  arm  are  controlled  by  two  cams  located  on  the  end  of 
the  camshaft.  The  small  collet  chuck  located  inside  of  part  M 


Fig.  9.   Tap  and  Die  Revolving  Attachment 

is  opened  by  the  engagement  of  a  small  pin  which  comes  into 
contact  with  a  stationary  rod  P.  The  work  is  then  ejected 
from  the  chuck  by  means  of  a  small  plunger  which  engages 
finger  R  when  the  transfer  arm  drops  back  preparatory  to 
receiving  another  piece. 

Tap  and  Die  Revolving  Attachment.  —  When  a  series  of 
operations  requires  no  other  slow  movement  except  the  reduc- 
tion of  speed  for  a  threading  operation,  the  tap  and  die  revolv- 
ing attachment  shown  in  Fig.  9  is  used  in  connection  with 
Brown  &  Sharpe  machines.  This  attachment  provides  means 
for  reducing  the  speed  of  the  tap  and  die  relative  to  the  work, 
when  threading,  and  of  increasing  the  speed  when  removing  a 


REAMING  ATTACHMENT 


207 


tap  or  die  from  the  threaded  part,  without  altering  the  speed 
of  the  work-spindle.  This  is  effected  by  revolving  the  tap  or 
die  in  the  same  direction  as  the  spindle,  but  at  a  slower  speed, 
the  combination  of  the  two  speeds  giving  the  desired  result. 
The  attachment  is  driven  by  a  belt  B  from  the  countershaft 
through  pulley  C  and  bevel  gears  D.  The  spring  E  acts  in  the 
same  manner  as  the  spring  in  an  ordinary  draw-out  die  or 
tap-holder. 

Accelerated    Reaming    Attachment.  —  For    reaming    holes 
which  exceed  in   depth   the  travel   of   the  end- working   tool- 


MacMncry 


Fig.  10.   Accelerated  Reaming  Attachment 

slide,  the  accelerated  reaming  attachment  shown  in  Fig.  10 
is  used  on  the  Acme  multiple-spindle  machine.  This  attach- 
ment is  held  in  the  " fourth"  end  position  in  the  tool-slide, 
and  consists  of  the  regular  cast-iron  collet  A  which  fits  in  the 
hole  in  the  tool-slide.  The  reamer  holder  C  is  a  sliding  fit  in 
the  steel  bushing  B,  and  is  furnished  with  a  loose  cap  D  in 
which  the  reamer  is  held  by  the  set-screw  shown.  The  cap  D 
is  held  to  the  holder  C  by  two  shoulder-head  screws,  the  bodies 
of  which  are  -5%  inch  smaller  in  diameter  than  the  holes  in  the 
cap,  thus  allowing  the  cap  to  " float"  a  slight  amount.  A 
stud  E  screwed  into  the  shank  of  the  holder  C  and  working 


208  ATTACHMENTS 

in  an  elongated  slot  in  the  bushing  and  collet  projects  through 
from  the  under  side  of  the  collet  and  works  in  an  elongated 
slot  in  the  lever  F.  This  lever  is  fulcrumed  on  a  screw  which 
is  located  in  either  holes  G  or  H,  depending  upon  the  excess 
amount  of  travel  required,  and  it  serves  to  accelerate  the  travel 
of  the  reamer.  In  order  to  increase  the  travel,  the  screw  is 
placed  in  hole  H,  and,  to  reduce  the  travel,  the  lever  is 
moved  back  so  that  the  screw  would  take  the  G  position. 
The  bracket  /  in  which  the  lever  is  fulcrumed  is  fastened 


Fig.  11.  Acme  Cross-drilling  and  Milling  Attachment  with  Spindles 
located  at  Right  Angles 

to  collet  A  and  advances  with  the  end- working  tool-slide. 
The  rear  end  of  lever  F  is  provided  with  two  hardened  screws 
rounded  on  the  heads,  which  come  in  contact  with  the  dogs 
J  and  K  when  the  device  is  in  operation.  These  dogs  are  ad- 
justable on  the  bracket  L,  fastened  to  the  gib  If,  which,  in 
turn,  is  held  to  the  bed  of  the  machine.  In  operation,  as  the 
end-working  tool-slide  advances,  the  round-headed  screw  in 
the  front  face  of  the  lever  comes  in  contact  with  dog  /,  and, 
as  the  tool-slide  continues  to  advance,  this  dog  acts  upon  the 
fulcrumed  lever,  drawing  out  the  reamer  holder  and  accelerat- 


MILLING  ATTACHMENTS  209 

ing  its  movement.  The  position  of  dog  /  on  the  bracket,  and 
also  the  location  of  the  screw  in  holes  G  or  H,  determines  the 
amount  of  excess  movement  given  to  the  reamer.  When  the 
tool-slide  drops  back,  dog  K  returns  the  reamer  holder  by  means 
of  lever  F  to  its  "back"  position. 

Drilling  and  Milling  Attachment.  —  A  two-spindle  drilling 
and  milling  attachment  in  which  the  spindles  are  located  at 
right  angles  to  each  other  is  shown  .in  Fig.  n  applied  to  an 
Acme  machine.  This  attachment  is  used  for  drilling  a  cross  hole 
and  milling  a  flat  on  the  work.  The  casting  C  which  carries 
the  spindles  A  and  B  is  fastened  to  the  top  face  of  the  cut-off 
tool-slide,  and  >  carries  a  pulley  D  which  is  driven  through  a 
flat  belt  from  a  special  overhead  countershaft.  Pulley  D  is 
keyed  to  the  top  horizontal  shaft  and  drives  the  vertical  mill- 
ing spindle  through  bevel  gears  E.  On  the  rear  end  of  the  top 
horizontal  shaft  is  a  spur  gear  F  which,  through  the  inter- 
mediate gear  G,  drives  the  spur  gear  H  fastened  to  the  drilling 
spindle  A.  This  attachment  is  adjustable  longitudinally  on 
the  base  7,  the  latter  being  fastened  to  the  top  face  of  the 
cut-off  tool-slide.  The  attachment  can  be  provided  with  an 
accelerating  movement,  if  desired. 

Vertical-spindle  Milling  Attachments.  —  Fig.  12  illustrates 
an  Acme  vertical-spindle  slab  milling  attachment,  designed 
for  carrying  two  face-milling  cutters  A  and  B.  These  cutters 
are  held  on  the  vertical  spindle  C  and  are  separated  by  a  spac- 
ing washer  of  the  required  thickness.  The  attachment  is  held 
on  the  top  face  of  the  cut-off  tool-slide,  and  is  arranged  for 
milling  two  flats  on  a  cold-rolled  steel  piece,  which  is  turned 
out  at  the  rate  of  fifty-three  pieces  per  hour.  The  vertical 
spindle  C  is  driven  by  bevel  gears  (enclosed  in  the  guard  D) 
and  the  pulley  E,  the  latter  being  belted  to  a  special  counter- 
shaft. It  is  possible  to  drive  this  attachment  without  employ- 
ing a  special  countershaft,  by  connecting  it  directly  through  a 
telescopic  knuckle-joint  shaft  to  the  gears  driving  the  thread- 
ing spindle. 

Another  vertical-spindle  slabbing  attachment  somewhat 
similar  in  construction  to  that  just  described  is  shown  in 


2IO 


ATTACHMENTS 


Fig.  13.  In  this  case,  however,  two  end-milling  cutters  A 
and  B  are  used.  The  spindles  carrying  the  end-mills  are  driven 
from  a  special  countershaft  belted  to  pulley  C.  This  pulley 


Fig.  12.   Acme  Slab  Milling  Attachment 


Fig.  13.   Acme  Slab  Milling  Attachment  equipped  with  Two 
End-mills 

is  keyed  to  the  shaft  D  which  drives  the  vertical  shaft  E 
through  bevel  gears  enclosed  in  guard  F.  On  opposite  ends 
of  shaft  E  are  held  gears  G  and  H,  which  mesh  with  gears 
on  the  vertical  milling  spindles.  This  attachment  is  fastened 


MILLING  ATTACHMENTS 


211 


to  the  top  face  of  the  cut-off  tool-slide  and  is  operated  as 
previously  described. 

End-milling  or  Slotting  Attachment.  —  Fig.  14  illustrates 
an  Acme  end-milling  or  slotting  attachment  which  is  held  in 
the  third  position  and  driven  by  gears.  The  bevel  gear  A 
receives  power  from  the  regular  gears  that  are  provided  for 


Fig.  14.   Acme  Slotting  or  Milling  Attachment  held  in  Third  Posi- 
tion and  Driven  from  Gears  in  Second  Position  Tool-spindle 

driving  the  tools  held  in  the  second  position  tool-spindle. 
The  cutter  is  adjusted  for  depth  by  means  of  a  special  device 
on  the  rear  end  of  the  main  tool-slide.  This  attachment  is 
held  rigidly,  being  tied  to  both  second  and  third  position 
tool-spindles.  The  work-spindle  in  the  second  position  is 
stopped  when  the  end-milling  or  slotting  attachment  is  at  work. 
Independent  Cutting-off  Attachment.  —  The  attachment 
shown  in  Fig.  15  is  used  on  Cleveland  automatics  for  cutting 


212  ATTACHMENTS 

off  the  work  when  the  tools  on  the  rear  and  front  of  the  cross- 
slide  are  used  for  forming  operations.  This  attachment  con- 
sists primarily  of  a  swinging  arm  A  mounted  on  a  stud  which 
is  attached  to  the  spindle  head  of  the  machine.  The  cutting-off 
blade  is  mounted  in  a  holder  B,  at  the  forward  end  of  the 
swinging  arm  A  ;  the  holder  B  is  fulcrumed  on  a  bolt  C  which 
is  provided  with  a  locking  nut  on  the  opposite  side  for  clamp- 


Fig.  15.  Independent  Cut-off  Attachment  on  Cleveland  Automatic 

ing  the  tool-holder  in  the  desired  position.  The  proper  setting 
of  the  cutting-off  blade  is  secured  by  means  of  the  set-screws 
D  which  operate  against  a  pin  driven  into  the  arm.  To 
make  this  adjustment,  it  is  necessary  to  release  the  nut  on 
the  clamping  bolt  C.  This  attachment  is  operated  by  the 
cam  G  held  on  the  camshaft  F,  the  cam  being  adjustably 
mounted  on  the  disk  H,  as  illustrated.  This  cam  contacts 
with  a  roll  held  in  arm  A  and  gives  it  the  required  move- 
ment at  the  desired  time.  The  roll  is  carried  on  an  eccen- 
tric stud  for  fine  adjustment  of  the  cutting-off  blade.  The 


SPECIAL  ATTACHMENTS 


213 


blade  is  clamped  in  the  holder  by  two  clamping  bolts  as  illus- 
trated. 

Attachment  for  Forming  Squares  and  Hexagons.  —  An 
attachment  for  automatic  screw  machines  is  shown  in  Fig.  16 
which  is  used  for  cutting  flat  surfaces,  such  as  squares  and 
hexagons  or  other  polygons,  on  work  produced  from  a  bar, 
directly  in  place,  so  as  to  save  a  second  handling  of  the  work 
after  leaving  the  automatic  machine.  The  attachment,  as 
designed,  is  particularly  intended  to  be  applied  to  a  four- 
spindle  automatic  screw  machine,  and  provisions  are  included 


Machinery 


Fig.  16.   Attachment  for  Milling   Squares  and   Hexagons  while  Work  is 
Revolving  for  Other  Machining  Operations 

for  driving  a  milling  cutter  of  special  design,  by  means'  of 
which  flat  surfaces  are.  cut,  and  also  for  feeding  this  cutter  past 
the  revolving  work.  It  should  be  understood  that  the  work 
revolves  while  the  flat  surfaces  are  cut. 

The  attachment  shown  in  the  illustration  is  arranged  for 
cutting  a  hexagon  on  the  end  of  one  of  the  bars  in  the  machine, 
the  cutting  tool  being  the  cutter  A ,  provided  with  three  teeth. 
This  cutter  is  placed  on  a  supplementary  slide,  mounted  on 
the  work-carrying  head  of  the  machine,  and  is  fed  by  means 
of  a  leverage  system  adjustable  to  suit  the  requirements. 
When  the  device  is  in  operation,  the  work  and  the  cutter  re- 
volve in  the  same  direction  in  relation  to'  their  axes,  so  that 
at  the  cutting  point  the  directions  of  the  surfaces  which  are 


214 


ATTACHMENTS 


in  contact  are  opposite,  but  the  cutter  is  geared  to  revolve  at 
twice  the  speed  of  the  work  to  be  provided  with  the  hexagon, 
and,  as  the  cutter  has  three  cutting  points  and  revolves  very 
rapidly,  it  produces  a  polygon  with  six  equal  sides  when  it 
has  traversed  the  full  width  of  the  flat.  If  the  cutter  had  only 
two  points,  a  square  would  be  produced.  If  a  cutter  having 
only  one  point  were  used,  the  gearing  being  the  same,  two 
flats  only  would  be  produced,  and  the  remaining  portion  of 
the  circular  surface  would  remain  curved.  It  is  clear  that 


I  I         FORMING  TOOL  CROSS- 


Machinery 


Fig.  17.   Arrangement  of  Worm  Robbing  Attachment  on  Automatic  Screw 

Machine 

the  same  results  can  be  obtained  by  gearing  of  other  ratios 
than  2  to  i,  provided  the  number  of  teeth  in  the  cutter  is  se- 
lected to  suit  the  ratio  of  revolutions.  The  sectional  view 
shows  how  the  drive  is  transmitted  to  the  cutter  from  the 
main  drive  of  the  machine. 

When  any  devices  are  applied  to  automatic  machines  which 
in  a  certain  sense  belong  outside  of  the  original  field  of  the 
machine,  it  is  very  important  to  take  into  consideration 
whether  these  devices  require  a  stoppage  of  the  regular  func- 
tions of  the  machine,  and  thereby  rob  the  machine  itself 


SPECIAL  ATTACHMENTS  215 

of  the  efficiency  of  which  it  is  capable,  or  whether  these  extra 
devices  perform  their  work  simultaneously  with  the  per- 
formance of  certain  of  the  legitimate  functions  of  the  tool. 
In  the  former  case,  it  is  often  doubtful  whether  the  intro- 
duction of  such  devices  is  economical.  Stopping  an  auto- 
matic machine  for  such  operations  as  screw  slotting,  milling, 
etc.,  which  prevent  the  continuous  working  of  the  machine, 
is  sometimes  questionable  economy.  On  the  other  hand, 
if  the  devices  are  so  designed  that  operations,  which  of  neces- 
sity must  be  performed  on  the  machine,  can  still  be  carried 
on  while  the  device  performs  its  own  functions,  then  the 
introduction  of  such  devices  is  of  distinct  advantage.  With 
the  device  just  described,  the  work  is  provided  with  its  flat 
surfaces  while  it  still  continues  its  rotary  motion,  thus  per- 
mitting other  cutting  tools  to  perform  their  functions  without 
interference. 


Fig.  18.   Worm  to  be  Hobbed,  and  the  Hob 

Attachment  for  Robbing  Worm  and  Spiral  Gears.  —  An  at- 
tachment applied  to  a  National-Acme  automatic  screw  machine 
for  bobbing  worm  and  spiral  gears  from  blanks  formed  from 
bar  stock  is  shown  in  Fig.  17.  The  design  of  the  worm  is  such 
that  it  could  not  be  handled  by  a  circular  hob  fed  longitu- 
dinally ;  therefore,  a  drop  feed  is  used.  By  calculation,  it 
was  found  that  forty  teeth  would  give  a  hob  of  the  diameter 
that  would  clear  the  two  high  points  on  the  worm  blank, 
marked  A  and  B  in  Fig.  18,  and  this  number  of  teeth  on  the 


216 


ATTACHMENTS 


hob  determines  the  entire  gearing  of  the  attachment.  The 
worm  being  of  the  single- threaded  type,  and  the  hob  used  to 
produce  it  having  forty  teeth,  it  follows  that  the  worm  must 
make  forty  revolutions  to  one  revolution  of  the  hob.  Now 
the  chucking  spindle  holding  the  worm  blank  must  make 
forty  revolutions  to  one  revolution  of  the  hob,  which  is  driven 
by  an  extra  shaft  geared  to  the  center  spindle  of  the  machine 
at  the  back  or  pulley  end.  Having  the  ratio  between  the  speed 
of  the  chucking  spindle  and  the  center  spindle,  which  in  this 
case  is  29  to  36,  the  shaft  B  in  Fig.  17  must  revolve  at  the  same 
speed  as  the  chucking  spindle.  The  40  to  i  reduction  is  ob- 
tained through  the  worm  on  this  shaft  and  the  worm-wheel 
on  the  hob  spindle.  In  Fig.  17,  D  shows  the  worm-wheel  and 

C  the  worm  keyed  on  the 
shaft  B.  On  the  No.  53 
machine  fitted  up  for  this 
job,  a  29-tooth  pinion  on 
the  center  spindle  drives 
a  3  6- tooth  gear  on  each 
chucking  spindle.  There- 
fore, a  29-tooth  pinion  is 
keyed  on  the  center  spindle  on  the  back  end  of  the  machine 
and  drives  a  3 6- tooth  gear  on  the  shaft  B  with  any  idler 
between  that  conveniently  meshes  with  the  two  gears. 

This  attachment  is  so  designed  that  the  hob  starts  hobbing 
the  worm  as  soon  as  the  forming  tool  begins  ^to  form  the  blank. 
Since  the  worm  C  and  the  worm-wheel  D  drive  the  hob  at 
the  required  speed,  and  as  their  relative  positions  cannot  be 
changed  without  altering  the  speed  of  the  hob,  it  is  evident 
that  the  center  of  the  worm  C  must  be  the  center  about  which 
the  hob  spindle  oscillates.  The  worm  can  drive  the  worm- 
wheel  D  keyed  on  the  hob  spindle  at  the  same  speed  in  any 
position  of  the  hob.  The  hob  spindle  is  carried  in  bearings 
on  an  independent  plate  H  which  swings  back  and  forth 
about  the  center  of  C,  on  the  surface  of  the  casting  I  that  is 
bolted  down  on  the  screw-machine  head.  A  cam  E  is  mounted 
on  the  forming  tool  cross-slide  to  raise  and  lower  the  hob.  An 


Machinery 


Fig.  19.   Detail  of  the  Feed  Cam 


SPECIAL  ATTACHMENTS  217 

arm  on  the  casting  H  has  a  roll  F  that  fits  in  the  cam  E,  and 
thus  the  raising  of  roll  F  by  cam  E  lowers  the  hob,  and  vice  versa. 

Fig.  19  shows  the  cam  E  more  clearly.  From  B  to  A,  the 
cam  lets  the  hob  drop  quickly  down  to  the  surface  of  the 
worm,  and  this  drop  occurs  when  the  cross-slide  of  the  ma- 
chine moves  in  quickly  until  the  forming  tool  starts  to  cut. 
This  action  of  the  cross-slide  reduces  the  time  required  to 
feed  in  by  sliding  in  quickly  to  the  point  where  the  forming 
tool  begins  to  cut.  The  tool  then  has  more  time  to  feed  in 
and  do  the  forming  at  a  slower  feed,  thus  producing  a  more 
perfectly  finished  blank.  For  this  reason,  the  cross-slide  was 
selected  to  feed  the  hob  on  this  attachment,  and  obtain  the 
same  action  for  the  feed  of  the  hob  as  for  the  feed  of  the  form- 
ing tool.  When  the  roller  F  has  passed  up  the  sharp  incline 
By  the  cross-slide  is  just  beginning  to  feed  in  slowly  and  the 
hob  is  just  touching  the  blank ;  then  the  roller  starts  up  the 
incline  A  at  a  slow  speed,  thus  feeding  the  hob  down  into 
the  blank  to  the  required  depth  at  a  very  slow  feed.  No 
spring  or  weight  is  required  to  lift  the  hob  out  of  the  hobbed 
worm,  as  the  cam  C  performs  this  function  by  lifting  the  hob 
high  enough  to  clear  the  chucking  spindle  of  the  machine, 
which  carries  the  hobbed  worm,  allowing  it  to  swing  around  a 
quarter  of  a  revolution  to  its  next  position  for  the  drilling 
operation. 

Not  being  certain  of  the  accuracy  of  the  scaled  dimensions 
of  positions  of  the  parts  of  the  machine  and  the  outside  diameter 
of  the  worm  being  subject  to  a  change,  the  cam  E  (Fig.  17) 
was  made  adjustable.  By  sliding  it  in  or  out  by  means  of  the 
screw  /,  various  diameters  of  a  o.oQS-inch  lead  single- threaded 
worm  may  be  hobbed,  providing  that  the  variation  does  not 
amount  to  enough  to  change  the  spiral  angle  sufficiently  to 
interfere  with  the  angle  of  the  teeth  cut  in  the  hob.  However, 
considerable  variation  in  the  diameter  of  the  worms  to  be 
hobbed  can  be  taken  care  of.  The  face  of  the  hob  being  flat 
and  tangent  to  the  worm,  there  is  considerable  clearance 
between  the  sides  of  the  teeth  on  the  hob  and  the  sides  of  the 
threads  on  the  worm  in  back  of  the  cutting  surface  of  the 


218 


ATTACHMENTS 


hob.  This  clearance  increases  as  the  curvature  of  the  worm 
is  farther  from  the  toothed  face  of  the  hob.  This  is  evident, 
in  that  the  teeth  become  narrower  at  the  top,  and  the  space 
between  becomes  wider.  The  hob  spindle  is  made  adjustable 
to  compensate  for  the  re-grinding  of  the  hob.  By  loosening 
the  nuts  on  the  back  end  of  the  spindle  from  the  steel  thrust 


Fig.  20.   Tilting  Magazine  Attachment 

collar,  the  clearance  may  be  taken  up  by  tightening  the  lock- 
nut  on  the  hob  end,  thus  pulling  the  spindle  forward. 

To  make  the  generating  hob,  another  hob  is  required  to 
cut  the  teeth,  this  hob  being  similar  to  the  one  used  in  hobbing 
a  worm-wheel.  In  fact,  the  relation  between  these  two  hobs 
is  the  same  as  between  a  worm  and  worm-wheel.  This  hob 
for  producing  the  teeth  in  the  generating  hob  used  on  the 
fixture  is  made  to  the  same  dimensions  as  the  worm  to  be 
hobbed.  It  is  thus  evident  that  the  generating  hob  will  repro- 
duce a  worm  of  the  same  form  of  thread  as  that  of  the  hob  that 


MAGAZINE  ATTACHMENTS 


2I9 


produced  the  teeth  in  it.  There  is,  however,  a  slight  exception 
in  this  case,  in  that  the  hob  takes  a  drop  cut  in  the  worm  blank, 
thereby  leaving  a  curve  on  the  threaded  length  of  worm  with 
a  radius  equal  to  half  the  diameter  of  the  hob  —  in  other  words, 
producing  a  worm  somewhat  of  the  Hindley  form.  No  ad- 
vantage in  this  shape  of  worm  is  gained,  however,  as  the  worm- 
wheel  driven  by  the  worm  is  much  smaller  in  diameter  than 
the  generating  hob. 


Fig.  21.   Vertical  Hopper  Magazine 

Magazine  Feeding  Attachments.  —  Magazines  for  han- 
dling work  to  be  chucked  automatically  have  developed  along 
many  lines,  and  a  great  number  of  ingenious  devices  have  been 
designed  which  are  adapted  to  the  various  shapes  and  kinds 
of  work  that  are  operated  upon  in  automatic  machines.  The 
attachments  shown  in  Figs.  20  to  23,  inclusive,  have  been  de- 
signed for  the  Cleveland  automatics.  What  is  known  as  a 
" tilting  magazine  attachment"  is  shown  in  Fig.  20.  This 
attachment  is  designed  for  handling  castings,  drop-forgings, 


22O 


ATTACHMENTS 


and  other  parts  requiring  a  second  operation.  The  magazine 
A  is  filled  from  the  top,  the  parts  being  placed  one  upon  the 
other.  In  the  illustration,  the  magazine  is  shown  tilted  down- 
ward, so  that  the  conveyor  B  is  in  a  position  to  advance  and 
secure  one  of  these  pieces.  After  a  part  is  removed  from  the 
magazine  by  the  conveyor,  the  magazine  tilts  upward  about 
shaft  C,  so  that  it  is  out  of  the  way  of  the  turret  tools ;  the 
conveyor  is  then  brought  into  line  with  chuck  D  into  which  the 


Fig.  22.   Rotary  Magazine  Attachment 

part  is  deposited.  The  tools  in  the  turret  and  those  on  the  cross- 
slide  then  proceed  to  machine  the  part  held  in  the  chuck. 
(No  tools  are  shown  in  this  particular  illustration.)  The  maga- 
zine frame  is  provided  with  adjustable  strips  and  bushings  to 
accommodate  parts  of  different  size.  The  finished  pieces  are 
automatically  removed  by  an  ejector  inside  of  the  machine 
spindle. 

Vertical  Magazines.  —  A  vertical  hopper  magazine  for  feed- 
ing studs  into  the  rear  end  of  the  spindle  of  a  Cleveland  auto- 
matic machine  is  shown  in  Fig.  21.  This  might  be  called  a 


MAGAZINE  ATTACHMENTS 


221 


"reservoir  magazine,"  as  it  has  a  widened  upper  portion  for 
carrying  a  large  number  of  parts.  The  work  feeds  by  gravity 
into  bushing  A,  and  it  is  forced  into  the  spindle  by  means  of 
a  push-rod  B,  which  is  operated  from  the  cam-drum  at  the 
rear  of  the  magazine.  There  is  an  agitator,  which,  by  means 


Fig.  23.   Front  View  of  Rotary  Tilting  Magazine 

of  a  cam-and-lever  mechanism,  oscillates  the  agitator  shaft  C 
which  insures  feeding  the  work  from  the  hopper.  The  magazine 
holds  from  300  to  1500  pieces,  the  number  depending  upon  the 
diameter,  and  the  entire  frame  is  adjustable  to  suit  any  length 
within  its  capacity. 

Rotary    Magazine    Attachment.  —  The    rotary    attachment 
shown  in  Fig.  22  is  intended  for  irregular-shaped  parts  which 


222  ATTACHMENTS 

cannot  be  fed  through  a  tilting  magazine.  The  pieces  are 
placed  by  hand  in  the  bushing  C  of  the  magazine.  The  illus- 
tration shows  a  piece  of  work  A  which  has  been  removed  from 
one  of  the  bushings  C  when  the  turret  was  in  its  forward  posi- 
tion; this  part  will  be  placed  in  the  chuck  when  the  turret  is 
indexed  so  as  to  bring  the  turret  into  alignment  with  the 
spindle.  The  magazine  is  indexed  by  a  dog  on  the  camshaft 
B  at  the  rear,  this  indexing  movement  occurring  before  the 
conveyor  is  in  position  to  take  another  casting  from  the  maga- 
zine ;  the  latter  is  locked  in  position  by  a  spring  plunger  after 
indexing.  The  work  is  removed  from  the  chuck  by  an  ejector 
after  being  finished. 

Rotary  Tilting  Magazine.  —  The  rotary  type  of  tilting  maga- 
zine, shown  in  Fig.  23,  is  used  for  second-operation  work.  The 
magazine  tilts  to  the  working  position,  as  shown  in  the  illus- 
tration, and,  after  the  piece  has  been  removed,  it  rises  to  clear 
the  turret  tools.  In  this  respect,  it  is  similar  to  the  tilting 
magazine  shown  in  Fig.  20,  but  differs  from  this  design  in 
that  the  parts  to  be  machined  are  placed  in  the  bushings  A 
which  are  mounted  in  the  links  B.  This  arrangement  permits 
of  handling  a  greater  variety  of  irregular  shaped  parts  than 
was  possible  with  the  original  form  of  magazine,  where  the 
parts  were  laid  one  upon  the  other  and  guided  by  parallel 
bars.  The  chain  composed  of  the  links  B  is  indexed  by  means 
of  the  lower  pair  of  sprocket  wheels  C,  one  of  which  is  pro- 
vided with  a  series  of  pins  that  engage  an  index  pawl  —  not 
shown  in  the  illustration.  This  pawl  rotates  the  sprockets 
upon  the  downward  tilt  of  the  magazine  and  brings  each  link 
B  in  line  with  the  conveyor  D  in  the  turret  hole ;  upon  the 
upward  tilt,  the  pawl  drops  down  and  engages  the  pin  follow- 
ing the  one  that  has  acted  upon  it.  The  sprocket  shaft  E 
rests  in  the  saddle  F  on  the  main  supporting  arm  G,  which 
serves  as  a  stop  and  also  maintains  the  required  alignment 
while  the  conveyor  is  removing  the  part  to  be  machined. 
The  adjustable  stop  H  mounted  on  the  main  supporting  arm 
prevents  the  conveyor  straining  the  magazine  while  removing 
the  work  from  the  bushing. 


MAGAZINE  ATTACHMENTS  223 

The  operation  shown  in  Fig.  23  is  the  machining  of  cast- 
iron  bushings  having  a  collar  or  shoulder  at  one  end.  In  this 
case,  the  part  that  is  gripped  in  the  chuck  is  cut  off  by  the  in- 
dependent cutting-off  attachment  /.  Occasionally,  when  the 
magazine  is  used  for  some  odd-shaped  piece  that  has  surface 
enough  to  grip  in  the  chuck,  it  is  necessary  to  employ  a  simple 
form  of  latch  held  by  a  spring  to  keep  the  piece  from  falling 
out.  This  statement  applies  only  to  second-operation  work 
and  is  referred  to  in  order  to  show  that  the  magazine  may  be 
employed  for  practically  any  shaped  piece  upon  which  a  second 
operation  must  be  performed.  Aside  from  the  tools  required 
for  different  jobs,  the  only  special  equipment  necessary  is 
bushings  of  the  required  size. 


CHAPTER  VII 
DESIGNING  SCREW  MACHINE  CAMS 

WHEN  an  automatic  screw  machine  is  equipped  with  special 
cams  for  controlling  the  movements  of  the  various  tools  and 
parts  of  the  machine  requiring  a  change  of  action,  whenever  a 
different  class  of  work  is  to  be  produced,  the  designing  of  these 
cams  constitutes  an  important  part  of  screw  machine  practice. 

As  the  preceding  descriptions  of  different  screw  machines 
indicate,  some  types  do  not  require  special  cams  for  producing 
different  parts,  but  are  so  arranged  that  the  necessary  changes 
of  feed  for  the  tools,  etc.,  are  obtained  either  by  adjustable 
cams  forming  a  permanent  part  of  the  machine  or  by  adjust- 
ments which  vary  the  motion  of  cams  that  are  a  part  of  the 
regular  equipment.  When  a  machine  is  designed  to  use  special 
cams,  the  advantages  aimed  at  are  the  securing  of  the  ideal 
conditions  as  to  rates  of  feed  for  each  operation,  and  the 
minimum  time  for  idle  movements;  such  cams  enable  the 
machine  to  duplicate  readily  the  same  part  at  any  future  time, 
the  cams  being  marked  and  preserved  for  this  purpose.  /The 
following  description  of  the  general  method  of  procedure  in 
designing  cams  applies  especially  to  the  Brown  &  Sharpe  auto- 
matic screw  machines,  although  a  study  of  the  principles 
involved  will  prove  of  value  in  connection  with  the  design  of 
cams  for  screw  machines  made  by  other  manufacturers. 

On  the  Brown  &  Sharpe  automatic  screw  machines,  three 
cams  constitute  a  set.  What  is  known  as  the  "front-slide 
cam"  operates  the  front  cross-slide,  the  " back-slide  cam" 
operates  the  back  cross-slide,  and  the  "lead  cam"  controls 
the  movement  of  the  turret  slide.  The  motion  for  feeding  the 
stock,  revolving  the  turret,  and  reversing  the  spindle  is  taken 
from  a  rear  driving  shaft  which  runs  at  a  constant  speed.  This 
shaft,  through  suitable  change-gears,  rotates  the  shafts  upon 

224 


GENERAL   PROCEDURE  225 

which  the  cross-slide  and  turret  operating  cams  are  mounted, 
at  a  speed  suitable  for  the  work  to  be  performed.  The  dura- 
tion of  the  cycle  of  operations  or  the  length  of  time  required 
to  make  one  piece  is  positively  regulated  by  means  of  these 
change-gears.  When  designing  cams,  it  is  well  to  bear  these 
essential  points  in  mind. 

Effect  of  Cutting  Speed  on  Cam  Design.  —  Before  the  cams 
are  laid  out,  it  is  necessary  to  decide  what  types  of  tools  are 
to  be  used  and  the  successive  order  of  the  operations.  Then 
the  cutting  speed  for  the  material  to  be  operated  upon  should 
be  determined  in  order  to  ascertain  the  speed  of  the  spindle. 
The  tool  movement  that  will  be  necessary  in  a  given  time  in 
order  to  secure  a  certain  rate  of  feed  per  revolution  must  also 
be  determined.  The  rise  of  each  cam  lobe  is  then  proportioned 
according  to  the  number  of  revolutions  which  the  spindle  and 
work  make  while  the  tool  controlled  by  that  particular  cam 
is  taking  its  cut. 

When  turning  parts  from  iron  or  steel,  the  formed  tools  will 
withstand  a  much  higher  speed  than  a  tap  or  die,  which  should 
be  taken  advantage  of  in  order  to  operate  the  machine  as 
economically  as  possible.  It  is  common  practice  to  run  the 
spindle  backwards  at  a  comparatively  fast  speed  for  the  form- 
ing and  cutting-off  operations,  and  forward  at  a  somewhat 
slower  speed  for  thread  cutting  and  other  operations  which 
can  be  performed  to  advantage  at  slower  speeds;  however,  if 
the  machine  is  to  be  used  for  a  variety  of  work,  or  if  hollow 
mills  or  box-tools  are  used  principally,  the  correct  speed  for 
a  die  or  tap  can  be  obtained  by  means  of  an  attachment  which 
serves  to  revolve  the  die  or  tap  in  the  same  direction  as  the 
spindle,  but  at  one-half  the  spindle  speed.  This  tap  and  die 
revolving  attachment  is  of  especial  value  where  the  work 
requires  no  other  slow  movement  except  that  for  threading. 

General  Method  of  Designing  Cams.  —  As  the  rise  of  each 
cam  lobe  is  proportioned  according  to  the  number  of  revolutions 
made  by  the  spindle  while  that  part  of  the  cam  is  in  use,  the 
relation  between  the  spindle  revolutions  and  the  various  opera- 
tions is  first  determined.  The  total  number  of  revolutions 


226  CAM   DESIGN 

required  to  complete  one  piece  is  found  by  adding  together 
the  number  of  revolutions  for  each  cut,  the  number  for  each 
indexing  of  the  turret,  for  feeding  the  stock,  etc. ;  an  approxi- 
mate number  of  revolutions  may  also  be  added  for  clear- 
ance. In  determining  the  number  of  revolutions  for  each 
operation,  it  is  necessary  to  decide  what  the  feed  should  be  in 
each  case.  Assuming,  for  instance,  that  a  feed  of  0.006  inch 
per  revolution  would  be  about  right  for  rough  turning,  and 
that  there  is  a  length  of  0.630  inch  to  turn,  this  operation  would 
require  about  105  revolutions  of  the  spindle.  If  one-half 
second  were  necessary  for  indexing  the  turret,  and  the  spindle 
speed  is  about  noo  revolutions  per  minute,  approximately 
9  revolutions  of  the  spindle  would  be  required  for  indexing ;  in 
actual  practice,  probably  12  or  13  revolutions  would  be  allowed. 
In  the  same  way,  the  number  of  revolutions  for  the  finishing 
cut  and  also  for  the  succeeding  operations  would  be  deter- 
mined, the  number  required  for  indexing  being  added  between 
each  operation. 

The  time  required  for  the  complete  operation  is  next  de- 
termined by  dividing  the  total  number  of  revolutions  by 
the  number  of  revolutions  which  the  spindle  makes  per  second. 
Thus,  if  the  estimated  number  of  revolutions  for  machining 
the  work  is  406,  and  the  spindle  makes  18  revolutions  per  sec- 
ond, the  time  for  completing  the  piece  will  equal  406  -*-  18  =  23 
seconds,  approximately.  When  the  number  of  seconds  for 
completing  the  work  has  been  obtained,  the  revolutions  re- 
quired for  each  operation  are  converted  into  hundredths  of  the 
cam  circumference,  and  the  different  lobes  on  the  cam  are 
proportioned  according  to  the  number  of  revolutions  for  each 
operation. 

If  the  spindle  revolves  18  times  per  second,  and  23  seconds 
are  required  to  make  one  piece,  it  will  revolve  414  times  for 
each  part  produced,  which  agrees  closely  with  the  approximate 
estimate ;  therefore,  if  the  spindle  revolves  414  times  for 
machining  each  part,  or  for  one  revolution  of  the  camshaft, 
each  y^-0-  of  the  cam  periphery  represents  414  -r-  100  =  4.14 
revolutions  of  the  spindle.  If  105  revolutions  are  required 


GENERAL  PROCEDURE  227 

for  rough-turning,  that  portion  of  the  cam  for  operating  the 
turret,  when  the  rough-turning  tool  is  in  position,  will  extend 
over  105-^4.14=  26  spaces,  approximately,  or  -ffo  of  the 
circumference  of  the  cam.  This  part  of  the  cam  circumference 
is  then  laid  out  so  that  it  will  impart  the  required  movement 
to  the  tool. 

In  this  way,  the  operation  of  the  turret-slide  and  the  cross- 
slides  can  be  worked  out  in  conjunction  with  one  another, 
and  the  proper  feeds  for  each  operation  can  be  determined 
in  advance.  One,  two,  or  sometimes  three  pieces  of  work 
are  completed  in  one  revolution  of  the  cam,  so  that  the  various 
movements  of  one  of  the  slides  in  making  a  particular  piece 
are  laid  out  as  curves  around  the  cam;  these  curves  either 
occupy  the  whole  circumference  or  are  repeated  once  or 
twice,  according  to  the  number  of  pieces  produced  per  revolu- 
tion. 

Laying  Out  Cams  for  a  Screw.  —  The  method  of  laying  out 
cams  on  the  No.  oo  Brown  &  Sharpe  automatic  screw  machine, 
for  producing  the  screw  shown  in  Fig.  i,  will  be  described. 
These  screws  are  to  be  made  from  ^--inch  soft  machinery  steel 
stock.  The  tools  used  and  the  successive  order  of  operations 
are  as  follows:  i.  Rough- turn  the  body  of  the  screw  with  a 
hollow  mill.  2.  Finish- turn  the  body  of  the  screw  with  a  box- 
tool.  3.  Cut  a  thread  on  the  end  of  the  screw.  4.  Cut  off  the 
finished  screw  and  at  the  same  time  shave  under  the  head  and 
remove  the  burr  with  a  forming  tool. 

For  roughing  cuts,  a  properly  constructed  hollow  mill  is 
recommended.  Such  a  tool  will  cut  easier  if  the  cutting  edges 
are  inclined  so  that  they  form  a  slightly  conical  shoulder  rather 
than  one  which  is  square.  For  finishing,  the  best  results  are 
usually  obtained  with  a  box- tool.  Such  a  tool  also  has  the  ad- 
vantage of  a  wide  range  of  sizes  and  it  can  be  equipped  with 
two  or  more  cutters  for  turning  different  diameters. 

Speed  of  the  Spindle.  —  The  number  of  revolutions  of  the 
spindle  required  for  the  various  operations  will  necessarily 
depend  upon  the  kind  of  work  to  be  done  and  the  amount 
of  stock  to  be  removed.  In  this  case,  two  spindle  speeds  will 


228 


CAM  DESIGN 


be  employed  in  order  to  use  a  comparatively  high  speed  for 
some  of  the  operations.  By  referring  to  the  spindle  speed 
chart  accompanying  the  No.  oo  machine,  it  will  be  found  that 
a  speed  of  927  revolutions  per  minute  with  the  spindle  running 
forward  and  1273  revolutions  with  the  spindle  running  back- 
ward may  be  used  to  advantage  for  producing  the  screw 
shown  in  Fig.  i.  The  slower  speed  gives  a  surface  speed  of 
30  feet  per  minute  for  cutting  the  thread  and  a  surface  speed 
of  53  feet  per  minute  at  the  outside  of  the  stock ;  1273  revolu- 
tions per  minute  gives  a  surface  speed  at  the  outside  of  the 


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Fig.  1.  Diagram  illustrating  Relation  between  Tool  Lengths 
and  Travel  of  Turret 

stock  of  73  feet  per  minute;  therefore,  the  machine  will  be 
arranged  so  that  the  rough-turning,  finish-turning,  and  thread 
cutting  are  done  at  the  slower  speed,  and  backing  off  the  die, 
cutting  off  the  finished  screw,  feeding  the  stock,  etc.,  at  the 
higher  speed. 

Spindle  Revolutions  for  Turning.  —  When  different  spindle 
speeds  are  used  for  the  forward  and  backward  directions  of 
rotation,  the  total  number  of  revolutions  for  producing  the 
part  should  be  based  on  the  higher  speed.  In  order  to  deter- 
mine the  total  number  of  revolutions,  it  will  be  necessary  to 
find  out  how  many  spindle  revolutions  are  required  for  each 


GENERAL  PROCEDURE  229 

operation,  which,  in  the  case  of  cutting  tools,  depends  upon  the 
amount  they  feed  per  revolution.  As  the  turning  is  to  be  done 
at  a  comparatively  slow  speed,  the  feed  may  be  rather  coarse, 
o.oio  inch  being  selected  for  roughing  and  o.on  inch  for 
finishing.  Rough- turning  a  length  of  0.625  mcn  plus  o.oio 
inch  for  clearance,  and  with  a  feed  of  o.oio  inch  per  revolu- 
tion, will  require  about  63  revolutions  (0.635  -f-  o.oio  =  63). 
The  finishing  cut  with  an  advance  movement  of  0.635  mcn 
at  o.on  inch  per  revolution,  plus  a  dwell  equivalent  to  three 
revolutions  at  the  end  of  the  cut  for  finishing  the  shoulder, 
will  require  about  61  revolutions.  It  will  be  assumed  that 
both  the  roughing  and  the  finishing  cuts  are  to  be  taken  in 
62  revolutions. 

Number  of  Revolutions  for  Thread  Cutting.  —  To  find  the 
number  of  revolutions  for  cutting  the  thread,  determine  the 
number  of  threads  on  the  end  of  the  screw  by  multiplying 
the  number  of  threads  per  inch  by  the  threaded  length ;  thus 
48X0.25=  12.  Adding,  say,  two  revolutions  for  clearance, 
14  revolutions  will  be  required  for  cutting  the  thread  and 
14  revolutions  for  backing  the  die  off  of  the  threaded  end. 

Revolutions  for  Cutting  off  Finished  Screw.  —  In  deter- 
mining the  number  of  revolutions  for  cutting  off  the  finished 
screw,  the  question  of  feed  is  again  involved.  Cutting-off 
tools  can  be  fed  from  0.0012  to  0.0017  inch  per  revolution,  but 
the  feed  should  be  reduced  towards  the  latter  part  of  the  cut. 
Forming  tools  can  be  fed  from  0.0002  to  o.ooi  inch,  the  amount 
largely  depending  upon  the  width  of  the  formed  part.  It  will 
be  assumed  that  the  feed  in  this  case  is  to  be  0.0015  mcn-  Now 
the  total  movement  of  the  cutting-off  tool  equals  the  radius 
of  stock,  or  eV  inch  +  0.005  incn  f°r  clearance  +  dimension  x 
(see  Fig.  2),  which  depends  upon  angle  a  of  the  cutting  edge. 
The  reason  for  inclining  the  cutting  edge  is  to  sever  the  finished 
part  without  leaving  a  teat  or  rough  spot  in  the  center  of  the 
screw-head,  such  as  would  usually  be  left  by  a  tool  having 
a  cutting  edge  parallel  with  the  axis  of  the  work.  The  dimen- 
sion x  equals  the  width  y  of  the  blade  multiplied  by  the  tangent 
of  angle  a.  Fifteen  degrees  has  been  proved  to  be  a  suitable 


230 


CAM  DESIGN 


angle  for  tools  used  on  steel  and  iron,  whereas,  for  brass  or 
bronze,  a  somewhat  greater  angle,  varying  from  about  20  to 
25  degrees,  gives  better  results.  Assuming  that  the  cutting-off 
tool  is  0.035  mcn  wide  and  the  angle  of  the  cutting  edge  is 
15  degrees,  then  x  equals  o.oio  inch.  Therefore,  the  total 
movement  of  the  tool  equals  g7^,  or  0.1093  +  0.005  +  o.oio 
=  0.125  inch  approximately.  The  spindle  revolutions  required 
equal  0.125  -5-  0.0015  =  83  revolutions,  approximately.  (This 
number  will  be  reduced  to  81  revolutions  in  this  particular 
case,  for  reasons  to  be  explained  later.)  While  the  stock  is 
being  cut  off,  a  forming  tool  can  shave  under  the  head  and 


Fig.  2.   Inclined  Edge  of  Cutting-off  Tool 

remove  the  burr,  so  that  additional  spindle  revolutions  are 
not  required  for  this  part  of  the  work. 

Revolutions  while  Indexing  Turret.  —  On  the  No.  oo 
Brown  &  Sharpe  automatic  screw  machine,  the  time  required 
for  indexing  the  turret  is  one-half  second.  With  a  spindle 
speed  of  927  revolutions  per  minute,  there  will  be  about  15.5 
revolutions  per  second,  or  approximately  8  revolutions  during 
the  one-half  second,  for  indexing.  It  is  usually  advisable  to 
add  from  two  to  four  revolutions  to  the  actual  number  required 
for  indexing  the  turret  and  feeding  the  stock;  therefore, 
10  revolutions  should  be  allowed  for  indexing  at  the  slower 
speed. 

Spindle  Revolutions  based  on  Fast  Speeds.  —  As  previously 
mentioned,  when  there  is  a  variation  between  the  forward 
and  backward  spindle  speeds,  the  number  of  revolutions  for 
each  operation  which  is  considered  in  designing  a  cam  is  based 


GENERAL  PROCEDURE 


231 


upon  the  fast  speed.  In  Table  I,  the  various  operations  for 
producing  the  screw  shown  in  Fig.  i,  and  the  corresponding 
number  of  spindle  revolutions  in  each  case,  are  listed  in  the 
successive  order.  The  column  headed  "  Spindle  Revolutions 
for  Each  Operation"  shows  the  actual  number  of  spindle  revo- 
lutions for  making  one  screw;  the  next  column  shows  what 
the  spindle  revolutions  would  be  if  the  spindle  ran  at  1273 
revolutions  per  minute  continually.  On  all  operations  for 

Table  I.    Revolutions  of  Machine  Spindle  and  Hundred ths  of  Cam 
Circumference  for  Different  Operations 


Successive  Order  of  Operations 

Spindle 
Revolutions 
for  Each 
Operation 

Spindle 
Revolutions 
Based  on 
1273  R.  P.  M. 

Hundredths 
of  Cam 
Circumference 

E 

Index  turret  and  reverse  spindle  .  . 
Rough-turn  with  hollow  mill  
Index  turret 

10 

62 
10 

14 
84 

14. 

4 
25 

A 

=§r>i 

Finish-turn  with  box-tool 

62 

84 

2C 

Index  turret  

IO 

14. 

A 

:n  °> 

Run  threading  die  on 

14. 

2O 

6 

Run  threading  die  off  

14 

14 

4 

S^ 

Cut-off  with  back  tool 

81 

81 

24. 

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Shave  under  head  and  remove  burr 
with  form  tool  and  index  turret 
three  times  while  cutting  off 
Feed  stock  to  stop  

14. 

14 

4 

Total  number  of  revolutions  for 
making  one  screw  

277* 

57Qf 

IOO 

*  Actual  number  of  revolutions  for  making  one  screw. 

t  Number  of  revolutions  required  if  spindle  speed  were  1273  R.  P.  M.  con- 
tinually. 

which  the  slower  speed  of  927  revolutions  per  minute  is  em- 
ployed, the  spindle  revolutions  based  on  the  higher  speed 
of  1273  revolutions  per  minute  are  used  in  proportioning  the 
cam.  For  instance,  62  revolutions  per  minute  are  actually 
required  for  rough-turning  with  the  hollow  mill,  but  the 
hundredths  of  cam  circumference  used  for  this  operation  is 
based  on  84  revolutions  at  the  fast  speed.  The  relation 


232  CAM  DESIGN 

between  the  spindle  revolutions  at  the  fast  speed  and  the 
actual  number  at  the  slower  speed  corresponds  to  the  relation 
between  the  spindle  speeds;  thus, 

1273  X  62 

927  :  1273  : :  62  :  x ;  x  =  —          —  =  85  revolutions. 

927 

The  reason  why  84  revolutions  are  listed  in  Table  I  instead 
of  85,  and  the  reason  for  similar  modifications  will  now  be 
explained. 

Modification  of  Spindle  Revolutions  to  suit  Change-gears.  — 
After  the  number  of  spindle  revolutions  for  each  operation 
have  been  determined  and  they  have  been  added  together  to 
obtain  the  total  number,  the  next  thing  to  consider  is  the 
relation  between  this  total  number  and  the  numbers  that  can 
be  obtained  with  the  different  combinations  of  change-gears 
accompanying  the  machine.  As  the  total  number  of  revolu- 
tions for  producing  a  part  does  not  always  equal  the  number 
obtained  with  the  change-gears,  it  is  necessary  to  modify  the 
revolutions  for  the  different  operations  in  order  to  obtain  an 
exact  number  for  which  the  change-gears  are  suited.  In  this 
case,  the  revolutions  listed  in  Table  I  were  changed  slightly 
in  order  to  obtain  the  total  of  339,  because  Table  II  shows  that 
this  is  the  number  for  which  the  machine  should  be  geared. 
For  instance,  instead  of  allowing  85  revolutions  for  rough- 
turning  and  finish-turning,  84  revolutions  were  allowed ;  the 
number  of  revolutions  for  cutting  off  was  also  reduced  from 
83  to  81,  so  that  a  total  of  339  was  obtained.  The  effect  of 
these  changes  on  the  action  of  the  tools  is,  of  course,  very 
slight,  the  effect  being  to  change  the  feeding  movement  of  the 
tool  somewhat.  As  will  be  seen  by  referring  to  Table  II, 
the  number  339  is  found  in  the  column  headed  by  the  spindle 
speed  of  1273  revolutions  per  minute,  and,  opposite  339  at  the 
left-hand  side  of  the  table,  the  change-gears  to  use  are  listed. 
In  this  case,  there  should  be  a  3o-tooth  gear  on  the  driving 
shaft  and  a  48- tooth  gear  on  the  worm-shaft.  As  339  repre- 
sents the  total  number  of  revolutions  at  the  fast  spindle  speed 
required  to  make  one  piece,  339 -f-  21.2  (the  number  of  revo- 


GENERAL  PROCEDURE 

Table  II.    Change-gears  and  Data  for  Laying  Out  Cams, No.  oo 
Brown  &  Sharpe  Automatic  Screw  Machine 


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20 

30 

46 

60 

3 

322 

377 

442 

518 

607 

711 

833 

976 

11 

44 

1340 

15 

70 

1840 

48 

750 

20 

3° 

48 

60 

3 

3 

336 

394 

461 

540 

634 

742 

870 

1018 

II 

*4 

1398 

16 

^8 

1920 

50 

720 

6,-fo 

20 

30 

50 

60 

3 

Z 

410 

480 

503 

660 

723 

906 

1061 

12 

43 

1457 

17 

•7 

2OOO 

52 

692 

620 

20 

30 

60 

426 

499 

585 

686 

803 

942 

1103 

12 

93 

17 

/5 

2080 

54 

666 

600 

20 

30 

60 

3 

178 

443 

5i8 

608 

713 

834 

1146 

13 

43 

1573 

18 

»3 

2100 

642 

575 

20 

30 

60 

3 

392 

459 

630 

739 

86-i 

1015 

1188 

13 

93 

1631 

IV 

u 

224O 

58 

620 

550 

2O 

3° 

60 

3 

406 

476 

557 

653 

766 

896 

1051 

1231 

14 

42 

1690 

19 

io 

2320 

60 

600 

525 

30 

21 

54 

7° 

3 

420 

492 

576 

675 

792 

927 

1087 

1273 

14 

y* 

1748 

20 

[8 

2400 

J>3_ 

57' 

500 

3° 

2O 

54 

70 

3 

441 

517 

60^ 

709 

832 

973 

1141 

1337 

15 

J7 

1835 

21 

V 

2520 

70 

450 

20 

20 

40 

3 

1400 

574 

672 

788 

924 

1082 

1268 

1485 

17 

41 

2039 

23 

*) 

2800 

77 

467 

420 

20 

20 

44 

70 

3 

539 

631 

739 

866 

1016 

1190 

1395 

1634 

19 

15 

2243 

26 

28 

3080 

84 

428 

385 

20 

20 

48 

70 

3 

S88 

806 

945 

1109 

I2q8 

1522 

1782 

20 

89 

2447 

2» 

^7 

3360 

"  W 

355 

70 

7° 

3 

746 

874] 

1024 

I2OI 

I4O6 

1649 

1931 

22 

h1 

26si 

31 

06 

3640 

The  number  of  hundredths  given  is  always  sufficient  for  feeding  stock,  but  it  is 
usually  best  to  add  i-ioo  for  revolving  the  turret 

lutions  per  second)  =  16,   which  is   the  number  of  seconds 
required  to  make  a  piece. 

Proportioning  the  Cam  Circumference.  —  If  the  spindle 
revolves  339  times  while  making  one  screw  or  for  one  revolu- 
tion of  the  camshaft,  each  y-J -Q  of  the  cam  periphery  represents 


234 


CAM  DESIGN 


339-7-100=3.39  revolutions  of  the  spindle.  Then,  if  14 
revolutions  are  required  for  indexing,  the  part  of  the  cam  cir- 
cumference controlling  this  indexing  movement  will  extend 
over  14  -5-  3.39  =  approximately  4  spaces,  each  representing 
a  hundredth  of  the  cam  circumference.  Similarly,  if  84  revo- 
lutions are  required  for  rough-turning,  the  cam  circumference 
needed  for  this  operation  will  equal  84  -f-  3.39  =  25  hundredths, 
approximately.  In  this  way,  the  cam  surface  is  divided  in 
proportion  to  the  number  of  spindle  revolutions  necessary 


Fig.  3.   Templet  used  for  Laying  Out  Automatic  Screw 
Machine  Cams 

for  each  operation,  and  it  is  advisable  to  list  the  results  as 
shown  in  the  column  at  the  right-hand  side  of  Table  I. 

The  Cam  Blanks.  —  The  cam  blanks  used  on  the  Brown  & 
Sharpe  machines  are  made  from  solid  disks  of  mild  cold-rolled 
steel.  The  blanks  for  lead  cams  are  4!  inches  in  diameter  for 
throws  less  than  one  inch,  and  5  inches  in  diameter  for  throws 
over  one  inch.  The  blanks  for  the  cross-slide  cams  are  4! 
inches  in  diameter.  Each  cam  has  a  hole  J  inch  in  diameter 
and  ^f  inch  from  the  center,  which  is  used  for  locating  the  cam 


GENERAL  PROCEDURE 


235 


on  its  shaft.    This  hole  also  serves  as  a  zero  point  from  which 
all  the  divisions  are  started  when  laying  out  the  cam. 

Laying  Out  the  Cam.  —  Laying  out  a  cam  involves,  first, 
dividing  the  circumference  into  spaces  which  are  proportional 
to  the  number  of  spindle  revolutions  for  each  operation,  and, 
second,  in  giving  each  cam  division  or  lobe  a  curvature,  which 
will  impart  the  required  motion  to  the  cutting  tool  controlled 
by  each  division.  In  order  to  readily  locate  these  lobes  or 


68\ 


Fig.  4.   Cam  for  Controlling  Movements  of  Turret-slide 

divisions,  the  cam  circle  is  divided  into  one  hundred  equal 
parts,  and,  after  having  determined  the  hundredths  of  cam 
circumference  needed  for  each  operation,  the  division  points 
are  marked  off  accordingly.  For  locating  these  division  points, 
a  bristol-board  templet  of  the  same  diameter  as  the  cam  blank 
and  divided  into  one  hundred  equal  spaces,  as  shown  in  Fig.  3, 
will  make  it  unnecessary  to  space  each  cam  circle  separately. 
The  holes  in  the  templet  correspond  to  those  in  the  cam  blank 
and  facilitate  setting  the  templet  in  the  correct  position. 


236  CAM  DESIGN 

Laying  Out  the  Lead  Cam.  —  The  lead  cam  for  producing 
the  screw  shown  in  Fig.  i  is  illustrated  in  Fig.  4.  When  laying 
out  this  lead  cam,  begin  at  a  point  on  its  circumference  oppo- 
site, the  J-inch  hole,  the  zero  line  being  established  at  this  point. 
The  cam  should  be  laid  out  to  use,  as  nearly  as  possible,  the 
entire  circumference.  That  part  of  the  lead  cam  which  is 
not  used  is  cut  down  to  a  radius  r  of  if  inch.  The  contour 
of  the  lead  cam  or  the  shape  of  its  outline  is  governed  by 
three  factors:  i.  The  circumferential  space  to  be  allowed; 

2.  The  movement  to  be  imparted  to  the  cam  lever  and  tool ; 

3.  The  distance  that  the  tool  projects  from  the  front  side  of 
the  turret.    On  the  No.  oo  Brown  &  Sharpe  machine,  when  the 
roll  on  the  lever  of  the  lead  cam  is  at  the  highest  part  of 
the  cam,  the  distance  from  the  front  side  of  the  turret  to  the 
chuck  is   if  inch,  and  the  maximum  distance  between  the 
chuck  and  turret  is  3  inches,  the  two  positions  being  indi- 
cated in  Fig.  i  by  the  dotted  arcs.     In  many  cases,  the  tool 
projects  so  far  from  the  turret  that-  the  cam  lobe  controlling 
its  movement  must  be  laid  out  so  that  it  does  not  extend  out- 
ward to  the  full  diameter  of  the  cam  blank.    In  other  words, 
the  cam  lobe  is  so  located  with  relation  to  the  center  of  the  cam 
that  the  tool  in  the  turret  will  operate  at  the  required  distance 
from  the  chuck. 

To  determine  the  radial  distance  of  a  cam  lobe  from  the 
center  of  the  blank,  locate  on  a  center-line  the  nearest  and 
farthest  positions  of  the  turret  with  relation  to  the  spindle 
chuck,  as  shown  in  Fig.  i,  and  also  the  location  of  the  part  to 
be  produced.  Then  measure  the  distance  from  the  outward 
cutting  edge  of  the  turning  tool  (in  this  case,  a  hollow  mill 
for  the  roughing  cut),  when  the  tool  is  pushed  back  in  the  turret 
against  its  shoulder.  After  adding  about  |  inch  to  this  dimen- 
sion to  allow  for  clearance  and  adjustment  of  the  tool,  lay  off 
the  dimension  from  the  point  where  the  tool  ends  its  cut, 
towards  the  line  representing  the  forward  turret  position. 
As  shown  in  the  illustration,  the  dimension  marked  "Hollow 
Mill"  extends  about  £  inch  beyond  the  face  of  the  turret  when 
the  latter  is  in  its  extreme  forward  position ;  therefore,  the 


LAYING  OUT  LEAD   CAM  237 

cam  lobe  for.  opera  ting  this  tool  should  be  laid  out  so  that  its 
highest  point  is  at  least  |  inch  from  the  full  diameter  of  the 
cam  blank. 

Cam  Lobe  for  Roughing  Cut.  —  In  producing  the  screw 
shown  in  Fig.  i,  the  stock  is  first  fed  against  a  stop  in  the 
turret  and  then  the  latter  is  indexed.  This  indexing,  as  previ- 
ously determined  and  recorded  in  Table  I,  requires  4  hun- 
dredths  of  the  cam  circumference;  beginning  then  with  a 
zero  line  passing  through  the  J-inch  pin-hole  in  the  cam  blank 
and  using  the  templet  shown  in  Fig.  3,  four  spaces  or  hundred ths 
are  laid  out  on  the  circumference;  a  radial  line  marked  4 
should  then  be  drawn  through  this  point.  As  25  hundred  ths 
of  the  cam  circumference  is  required  for  the  roughing  cut, 
another  radial  line  is  drawn  29  hundredths  from  the  zero  line. 
The  spiral  cam  lobe  for  the  roughing  cut  is  then  laid  off  be- 
tween these  two  lines,  the  curve  starting  on  radial  line  4  and 
ending  on  line  29.  Now  it  was  found  by  means  of  Fig.  i  that, 
owing  to  the  length  of  the  hollow  mill  and  its  holder,  the  high- 
est part  of  this  cam  lobe  should  not  extend  to  the  outer  edge 
of  the  cam  blank  closer  than  f  inch;  therefore,  the  starting 
point  of  the  curve  at  a  is  a  radial  distance  in  from  the  edge 
of  the  blank,  equal  to  the  travel  of  the  tool  plus  f  inch.  As 
the  tool  is  to  have  a  uniform  feeding  movement,  the  cam  lobe 
is  laid  off  in  the  form  of  a  spiral,  or  so  that  it  has  a  uniform 
rise  from  the  cam  center.  The  way  in  which  this  curve  is 
obtained  is  indicated  by  the  illustration.  The  space  between 
the  radial  lines  4  and  29  is  divided  into  several  equal  divisions 
by  additional  radial  lines.  A  corresponding  number  of  equally- 
spaced  divisions  are  then  laid  off  on  line  0.635,  representing 
the  rise  of  the  cam,  by  means  of  circular  arcs.  The  points  of 
intersection  between  the  inner  arc  and  the  first  radial  line, 
the  next  successive  arc  and  the  second  radial  line,  etc.,  lie  along 
the  cam  curve,  which  is  drawn  through  these  points. 

Withdrawal  of  Turret  for  Indexing.  —  With  the  No.  oo 
machine,  one-half  second  is  required  for  the  indexing  move- 
ment and,  as  previously  determined,  4  hundredths  of  the  cam 
circumference  should  be  employed;  therefore,  a  radial  line 


238  CAM  DESIGN 

4  hundredths  from  line  29  is  located  and  marked  33,  which  repre- 
sents the  number  of  hundredths  from  the  zero  position.  The 
inclination  of  the  "line  of  drop"  b  depends  upon  the  speed 
at  which  the  cam  is  to  rotate.  In  this  case,  16  seconds  are 
required  to  make  one  screw,  so  that  the  cam  makes  one  com- 
plete turn  in  that  length  of  time.  On  this  machine,  if  a  part  is 
produced  within  from  6  to  35  seconds,  the  line  of  drop  may  be 
tangent  to  the  one-inch  hole  in  the  center  of  the  cam  blank. 
Cams  which  rotate  faster  require  an  easier  line  of  drop  or  one 
which  is  not  so  abrupt,  while  cams  which  revolve  at  a  compara- 
tively slow  speed,  as,  for  instance,  those  for  a  period  of  35 
seconds  or  over,  may  have  a  line  of  drop  which  is  radial. 
Templets  such  as  are  shown  in  Fig.  7  are  convenient  to  use  for 
constructing  both  the  rise  and  drop  on  cams.  These  templets 
have  several  lobes  representing  the  rise  and  drop  for  different 
cam  speeds  which  are  plainly  stamped  on  the  templet.  After 
drawing  a  line  b  (Fig.  4)  tangent  to  the  one-inch  hole,  describe 
an  arc  equal  to  the  radius  of  the  cam  roll.  This  arc  should  be 
tangent  with  line  b  and  located  radially  so  that  it  connects 
with  the  starting  point  of  the  next  cam  curve. 

Cam  Lobe  for  the  Finishing  Cut.  —  A  box-tool  is  to  be 
used  for  the  finishing  cut,  which  does  not  project  from  the  turret 
as  far  as  the  hollow  mill,  so  that  the  cam  lobe  in  this  case  may 
extend  to  the  outer  edge  of  the  cam  blank.  As  25  hundredths 
of  the  cam  circumference  are  required,  radial  line  58  is  drawn 
(33  +  25  =  58).  The  feeding  movement  of  the  tool  occurs  be- 
tween lines  33  and  57  and  then  there  is  a  dwell  of  i  hundredth, 
which  allows  the  tool  to  remain  stationary  for  a  moment  at 
the  end  of  its  cut,  in  order  to  finish  the  shoulder  or  under  side 
of  the  screw-head.  The  curve  for  this  part  of  the  cam  lobe 
begins  at  a  point  0.635  mcn  m  fr°m  the  edge  °f  the  cam  blank 
on  line  33,  as  this  dimension  represents  the  advanced  movement 
of  the  tool.  The  curve  between  lines  33  and  57  is  laid  out 
the  same  as  for  the  cam  lobe  between  lines  4  and  29. 

Cam  Lobe  for  Threading.  —  The  drop  for  allowing  the  turret 
to  withdraw  preparatory  to  indexing  is  laid  off  between  lines 
58  and  62,  the  same  as  previously  described  for  the  drop 


LAYING  OUT  LEAD   CAM  239 

between  lines  29  and  33,  and  then  the  cam  lobe  for  controlling 
the  movements  of  the  threading  die  is  constructed.  This  lobe 
is  given  a  rise  which  is  slightly  less  than  the  travel  of  the 
die,  so  that  the  latter  will  be  free  to  follow  the  pitch  of  the 
thread.  In  order  to  allow  this  freedom  of  movement,  the  die- 
holder  is  so  constructed  that  the  die  is  prevented  from  rotating 
with  the  work,  but  is  free  to  move  in  the  direction  of  its  axis. 
The  actual  rise  of  the  threading  lobe  or  cam  equals  the  number 
of  spindle  revolutions  required  for  threading,  divided  by  the 
number  of  threads  per  inch,  minus  from  10  to  15  per  cent 
(depending  upon  the  pitch  of  the  thread)  to  allow  the  turret 
to  lag  behind  the  die  slightly.  In  this  case,  there  are  48  threads 
per  inch  and  14  spindle  revolutions  are  needed  for  the  opera- 
tion, two  being  allowed  for  clearance ;  therefore,  the  rise  not 
allowing  for  a  reduction  equals  14  -f-  48  =  0.292  inch.  This 
rise  is  next  reduced,  say,  15  per  cent  or  to  0.250  inch,  and  the 
lobe  is  laid  out  between  radial  lines  62  and  68,  as  6  hundredths 
are  required  for  running  the  die  onto  the  work.  The  thread- 
ing lobe  is  then  given  a  drop  of  0.250  inch,  covering  4  hundredths 
more  of  the  cam  circumference.  The  exact  method  of  laying 
out  the  curve  of  a  threading  lobe  will  be  described  later. 

The  radial  position  of  this  threading  lobe  must  also  be  de- 
termined so  that  the  die  movement  will  be  in  the  required 
position  relative  to  the  work.  The  height  of  the  threading 
lobe  may  be  determined  by  the  same  method  previously 
described  in  connection  with  Fig.  i  for  the  hollow  mill.  The 
distance  that  the  face  of  the  die-holder  projects  beyond  the 
turret  is  measured  and,  after  allowing  a  slight  amount  for 
clearance,  this  distance  is  laid  off  on  the  center-line  from  the 
point  where  the  thread  ends,  as  indicated  by  the  dimension 
marked  " Die-holder."  If  the  die-holder  projects  ij  inch  from 
the  turret  and  -£$  inch  is  allowed  for  clearance,  the  dimension 
x,  or  f  inch,  will  represent  the  radial  distance  from  the  outer 
edge  of  the  cam  blank  to  the  top  of  the  threading  lobe. 

Unused  Part  of  Lead  Cam.  —  After  the  threading  operation 
is  completed  (see  Table  I),  the  cutting-off  and  forming  tools 
come  into  action  and  the  turret  is  not  required  until  the  fin- 


240 


CAM  DESIGN 


ished  part  has  been  severed  and  the  stock  is  fed  forward  against 
the  stop  in  the  turret  for  producing  a  new  piece.  That  part  of 
the  lead  cam  which  is  not  used  should  be  reduced  to  a  radius 
r  of  ij  inch.  This  concentric  part  of  the  cam  is  connected 
with  the  radial  lines  72  and  96  by  a  suitable  drop  and  rise. 
While  the  lead  lever  is  passing  thi$  reduced  part  of  the  cam 
surface,  and  the  cross-slide  tools  are  at  work,  the  turret  is 
indexed  three  times,  thus  skipping  the  two  holes  which  do  not 


Fig.  5..  Rear  Cross-slide  Cam 

contain  tools  and  bringing  the  stock  stop  around  into  align- 
ment with  the  spindle. 

Lobe  for  Stock  Stop.  —  The  lobe  for  the  stock  stop  is  lo- 
cated between  the  lines  96  and  o,  since  4  hundredths  of  the 
cam  circumference  are  required,  as  shown  by  Table  I.  This 
lobe  is  a  "dwell,"  which  means  that  it  is  concentric  and  holds 
the  turret  stationary  while  the  lead  lever  is  passing  over  it. 
The  height  of  this  lobe  is  determined  by  measuring  the  dis- 
tance that  the  stock  stop  projects  from  the  turret,  and  laying 
off  this  distance  as  indicated  by  the  line  marked  "Stop"  in 
Fig.  i.  If  the  stop  projects  iiV  inch  and  dimension  y  is  f 


LAYING  OUT  BACK-SLIDE  CAM 


24I 


inch,  then  the  concentric  surface  of  the  cam  lobe  should  be 
|  inch  in  from  the  outer  edge  of  the  blank,  as  shown  in  Fig.  4. 

After  laying  out  an  arc  between  the  zero  line  and  radial 
line  4,  having  a  radius  equal  to  the  radius  of  the  cam  roll,  the 
lay-out  of  the  cam  is  completed.  As  the  lead  lever  is  passing 
the  space  between  lines  o  and  4,  the  turret  is  indexed  to  bring 
the  hollow  mill  into  position  for  rough-turning  the  next  piece, 
and,  at  the  same  time,  the  spindle  rotation  is  reversed  and 


Fig.  6.   Front  Cross-slide  Cam 

reduced  to  the  slower  speed  used  for  the  turning  and  thread- 
cutting  operations. 

Laying  Out  the  Back-slide  Cam.  —  The  back-slide  cam, 
or  the  one  for  operating  the  rear  cross-slide,  is  illustrated  in 
Fig.  5.  As  shown  by  Table  I,  the  total  movement  of  the  cutting- 
off  tool  equals  0.125  inch,  which  equals  the  rise  of  the  cam 
lobe  between  the  radial  lines  72  and  96.  The  cutting-off  tool 
starts  at  line  72  or  as  soon  as  the  die  has  been  backed  off  of 
the  work,  as  indicated  by  line  72  of  the  lead  cam  (see  Fig.  4). 
The  quick  rise  a  of  the  back-slide  cam  is  given  a  radius  of 
ij  inch,  drawn  from  a  center  one-half  inch  from  the  outside, 


242 


CAM  DESIGN 


whereas  the  drop  line  b  is  tangent  to  the  one-inch  hole  in  the 
center.  These  two  lines  a  and  b  are  connected  to  the  concen- 
tric part  of  the  cam  by  curves  having  a  radius  of  J  inch  which 
corresponds  to  the  radius  of  the  cam-lever  roll.  As  previously 
explained,  the  quick  rise  and  the  drop  varies  for  different 
speeds  and  may  be  laid  out  directly  from  a  templet  similar 
to  the  one  shown  in  Fig.  7,  which  is  used  on  the  Nos.  oo  and 
ooG  Brown  &  Sharpe  automatic  screw  machines.  The  back- 
slide cam  lobe  ends  at  line  96,  24  hundredths  of  the  cir- 


Fig.  7.  Templet  for  Rise  and  Drop  of  Cams  used  on  Nos. 
00  and  OOG  Brown  &  Sharpe  Automatic  Screw  Machines 

cumference  being  utilized  in  connection  with  the  cutting-off 
operation.  The  4  hundredths  remaining  between  lines  96  and 
o  represent  the  time  allowed  for  feeding  the  stock.  That  part 
of  the  front-  and  back-slide  cams  which  is  not  used  is  laid  out 
to  a  radius  r  of  ij  inch. 

Laying  Out  the  Front-slide  Cam.  —  While  the  cutting-off 
tool  is  at  work,  a  forming  tool  is  used  to  shave  under  the  head 
of  the  screw  and  remove  the  slight  burr  left  by  the  cutting-off 
tool.  The  movement  required  for  the  forming  tool  is  equal 
to  the  difference  between  the  radius  of  the  screw-head  and  the 
radius  of  the  body,  plus,  say,  0.005  inch  for  clearance,  giving 
a  total  movement  of  0.036  inch.  Assuming  that  the  feed  of 


LAYING  OUT  FRONT-SLIDE  CAM 


243 


92  X 


\ 


A 


the  tool  is  to  be  0.0013  inch,  the  required  number  of  spindle 
revolutions  will  equal  0.036  -f-  0.0013  =27.7.  As  each  one 
hundredth  of  the  cam  circumference  is  equivalent  to  3.39 
spindle  revolutions,  8  hundredths  of  the  front-slide  cam  cir- 
cumference is  utilized  (27.7  -r-  3.39  =  8,  approximately).  The 
quick  rise  a  (Fig.  6)  and  the  drop  b  are  laid  off  as  previously 
described  in  connection  with  the  back-slide  cam.  The  forming 
tool  begins  work  at  line  72,  which  corresponds  with  the  point 
at  which  the  cutting-off 
tool  comes  into  action, 
these  two  tools  operating 
simultaneously.  After 
the  forming  tool  has 
been  moved  inward  0.036 
inch,  it  is  allowed  a  dwell 
of  one  hundredth  of  the 
cam  circumference,  so 
that  the  tool  can  remove 
the  burr  caused  by  the 
cutting-off  tool  when 
starting  in.  The  re- 
mainder of  the  cam  is 
made  to  a  radius  of  ij 
inch,  since  this  part  is 
not  used. 

Developing  Cam  Lobe  for  Threading  Operation.  —  When 
cutting  a  thread  on  the  Brown  &  Sharpe  automatic  screw 
machines,  the  die  is  started  on  the  work  by  the  threading 
lobe  on  the  lead  cam  which  actuates  the  turret-slide,  and  then 
the  die  movement  is  governed  by  the  lead  of  the  thread,  the 
turret  traveling  at  a  slightly  slower  rate.  If  the  cam  were 
laid  out  to  positively  control  the  movement  of  the  threading 
die,  unsatisfactory  results  would  be  obtained,  as  the  die  would 
be  crowded  at  times,  owing  to  the  fact  that  the  spindle  speed 
and  the  speed  of  the  driving  shaft  are  not  constantly  in  exactly 
the  same  ratio ;  therefore,  the  cam  lobe  is  laid  out  so  that  it 
gives  the  die  a  positive  start  when  cutting  the  first  two  threads, 


Machinery,  N.  7. 


Fig.  8.   Method  of  Constructing  Thread 
Lobe  on  Lead  Cam 


244  CAM  DESIGN 

and  then  the  cam  is  relieved  so  that  the  turret-slide  lags  be- 
hind slightly. 

Before  the  thread  lobe  can  be  constructed,  the  length  of 
the  threaded  portion,  the  number  of  threads  per  inch,  and  the 
total  number  of  revolutions  of  the  spindle  for  completing  one 
piece  must  be  determined.  The  rise  on  the  cam  may  then  be 
found  by  the  following  formulas : 

From  14  to  24  threads  per  inch,  r  =  (R  -f-  p)  X  0.85 
From  28  to  48  threads  per  inch,  r  =  (R  -r-  p)  X  0.88 
From  56  to  80  threads  per  inch,  r  =  (R  -f-  p)  X  0.90 
in  which, 

R  =  revolutions  required  for  threading ; 
*  p  =  number  of  threads  per  inch ; 
r  =  rise  on  cam. 

The  accompanying  tables,  "Spindle  Revolutions  and  Cam 
Rise  for  Threading,"  give  the  spindle  revolutions  for  thread- 
ing various  lengths  and  pitches,  and  the  corresponding  rise 
for  the  cam  lobe.  To  illustrate  the  use  of  these  tables,  suppose 
that  a  cam  is  to  be  laid  out  for  threading  the  screw  shown 
at  A,  Fig.  8,  on  a  No.  oo  Brown  &  Sharpe  automatic  screw 
machine.  Assume  that  the  spindle  speed  is  to  be  2400  revolu- 
tions per  minute ;  the  number  of  revolutions  to  complete  one 
piece,  400 ;  time  required  to  make  one  piece,  10  seconds ; 
length  of  the  threaded  portion,  |  inch;  pitch  of  the  thread, 
^2  inch,  or  32  threads  per  inch.  By  referring  to  Table  III, 
under  "32  threads  per  inch"  and  opposite  "f  "  (length  of 
threaded  portion)  the  number  of  revolutions  required  is  found 
to  be  15  and  the  rise  of  the  cam  lobe,  0.413  inch. 

To  construct  the  lobe,  convert  the  revolutions .  into  hun- 
dredths  ofccam  surface,  or  15  -f-  400  =  0.0375,  or  3!  hundredths. 
Then  draw  the  cam  circle  B,  as  shown  in  Fig.  8,  and  lay  off 
on  this  circle  3!  hundredths  to  advance  on  the  screw  and 
3!  hundredths  to  withdraw.  Locate  the  top  of  the  lobe  an 
amount  C  below  the  outer  cam  circle  B  as  required.  Bisect 
the  rise  at  E,  and,  with  OE  as  a  radius  and  a,  6,  and  c  as  centers, 
draw  arcs  intersecting  each  other  at  d  and  e.  With  d  as  a 


Table  III.    Spindle  Revolutions  and  Cam  Rise  for  Threading 


Length  of 
Threaded 
Portion 

Number  of  Threads  per  Inch 

64 

56 

48 

40    |    36   |   32 

30 

28 

24 

20     |     18 

16 

First  Line:  Revolutions  of  Spindle  for  Threading 
Second  Line:  Rise  on  Cam  for  Threading 

6.50 

6.  50|  4.50 

4.50 

4.00 

4.00|  4.00 

4.00 

3* 

0.091 

0.1040  082 

0.099 

0.098 

0.1100.117 

0.126 

8  50 

8  00 

6.00 

5.50 

5.50 

5.00   5.00 

5.00 

3.00 

A 

0.120 

0.129 

0.110 

0.121 

0.134 

0.138 

0.147 

0.157 

0.106 

10.50 

10.00 

7.50 

7.00 

6.50 

6.00 

6.00 

5.50 

4.00 

3.50 

A 

0.148 

0.161 

0.137 

0.154 

0.159 

0.165 

0.176 

0.173 

0.142 

0.149 

i 

12.50 

11.50 

9.00 

8.00 

7.00 

7.00 

7.00 

6.50 

4.50 

4.00 

3.50 

3.50 

t 

0.176 

0.185 

0.165 

0.176 

0.171 

0.193 

0.205 

0.204 

0.159 

0.170 

0.165 

0.186 

e 

14.50 

13.50 

10.50 

9.50 

8.50 

8.00 

7.50 

7.50 

5.50 

4.50 

4.00 

4.00 

/I 

0.204 

0.217 

0.192 

0.209 

0.208 

0.220 

0.220 

0.236 

0.195 

0.191 

0.189 

0.212 

0 

16.50 

15.00 

12.00 

10.50 

10.00 

9.00 

8.50 

8.50 

6.00 

5.50 

5.00 

4.50 

A 

0.232 

0.241 

0.2200.231 

0.244 

0.248 

0.249 

0.267 

0.213 

0.234 

0.236 

0.239 

7 

18.50 

17.00 

13.5012.00 

11.00 

10.00 

9.50 

9.00 

7.00 

6.00 

5.50 

5.00 

32 

0.260 

0.273 

0.247 

0.264 

0.269 

0.275 

0.279 

0.283 

0.248 

0.255 

0.260 

0.266 

1 

20.50 

18.50 

15.00 

13.00 

12.00 

11.00 

10.50 

10.00 

7.50 

6.50 

6.00 

5.50 

\ 

0.288 

0.297 

0.275 

0.286 

0.293 

0.303 

0.308 

0.314 

0.266 

0.276 

0.283 

0.292 

9 

22.50 

20.50 

16.50 

14.50 

13.00 

12.00 

11.50 

11.00 

8.50 

7.00 

6.50 

6.00 

A 

0.316 

0.329 

0.302 

0.319 

0.318 

0.330 

0.337 

0.346 

0.301 

0.298 

0.307 

0.319 

5 

24.50 

22.00 

18.0015.50 

14.50 

13.00 

12.50 

12.00 

9.00 

8.00 

7.00 

6.50 

TS 

0.345 

0.354 

0.3400.341 

0.354 

0.358 

0.367 

0.377 

0.319 

0.340 

0.330 

0.345 

1  1 

26.50 

24.00 

19.50!17.00 

15.50 

14.00 

13.50 

12.50 

10.00 

8.50 

7.50 

7.00 

71 

0.373 

0.386 

0.3570.374 

0.379 

0.385 

0.396 

0.393 

0.354 

0.361 

0.354 

0.372 

28.50 

25.50 

21.0018.00 

16.50 

15.00 

14.50 

13.50 

10.50 

9.00 

8.50 

7.50 

0.401 

0.410 

0.3850.396 

0.403 

0.413 

0.425 

0.424 

0.372 

0.383 

0.401 

0.398 

U" 

30.50 

27.50 

22.5019.50 

17.50 

16.00 

15.00 

14.50 

11.50 

9.50 

9.00 

8.00 

0.429 

0.442 

0.4120.429 

0.428 

0.440 

0.440 

0.456 

0.407 

0.404 

0.425 

0.425 

7 

32.50 

29.00 

24.0020.50 

19.00 

17.00 

16.00 

15.50 

12.00 

10.50 

9.50 

8.50 

iV 

0.457 

0.466 

0.440 

0.451 

0.464 

0.468 

0.469 

0.487 

0.425 

0.446 

0.448 

0.451 

1  5 

34.50 

31.00 

25.50 

22.00 

20.00 

18.00 

17.00 

16.00 

13.00 

11.00 

10.50 

9.00 

if 

0.484 

0.498 

0.477 

0.484 

0.489 

0.495 

0.499 

0.503 

0.460 

0.468 

0.496 

0.478 

i 

36.50 

32.50 

27.00 

23.00 

21.00 

19.00 

18.00 

17.00 

13.50 

11.50 

10.50 

9.50 

s 

0.513 

0.522 

0.495 

0.506 

0.513 

0.523 

0.528 

0.534 

0.478 

0.489 

0.496 

0.504 

i  7 

38.50 

34.50 

28.50 

24.50 

22.00 

20.00 

19.00 

18.00 

14.50 

12.00 

11.00 

10.00 

si 

0.541 

0.554 

0.522 

0.539 

0.538 

0.550 

0.557 

0.566 

0.514 

0.510 

0.519 

0.531 

9 

40.50 

36.00 

30.00 

25.50 

23.50 

21.00 

20.00 

19.00 

15.00 

13.00 

11.50 

10.50 

T* 

0.570 

0.579 

0.550 

0.561 

0.574 

0.578 

0.587 

0.597 

0.531 

0.553 

0.543 

0.558 

1  9 

42.50 

38.00 

31.50 

27.00 

24.50 

22.00 

21.00 

19.50 

16.00 

13.50 

12.00 

11.00 

H 

0.598 

0.611 

0.577 

0.594 

0.599 

0.605 

0.616 

0.613 

0.567 

0.574 

0.566 

0.584 

44.50 

39.50 

33.00 

28.00 

25.50 

23.00 

22.00 

20.50 

16.50 

14:00 

13.00 

11.50 

0.626 

0.635 

0.605 

0.616 

0.623 

0.633 

0.645 

0.644 

0.584 

0.595 

0.614 

0.611 

21 

46.50 

41.50 

34.50 

29.50 

26.50 

24.00 

23.00 

21.50 

17.50 

14.50 

13.50 

12.00 

If 

0.654 

0.667 

0.622 

0.649 

0.648 

0.660 

0.675 

0.676 

0.620 

0.616 

0.637 

0.637 

48.50 

43.00 

36.00 

30.50 

28.00 

25.00 

23.50 

22.50 

18.00 

15.50 

14.00 

12.50 

0.682 

0.691 

0.660 

0.671 

0.684 

0.688 

0.689 

0.707 

0.638 

0.659 

0.661 

0.664 

50.50 

45.00 

37.50 

32.00 

29.00 

26.00 

24.50 

23.00 

19.00 

16.00 

14.50 

13.00 

' 

0.710 

0.723 

0.677 

0.704 

0.709 

0.715 

0.719 

0.723 

C.673 

0.680 

0.684 

0.690 

52.50 

46.50 

39.00:33.00 

30.00 

27.00 

25.50 

24.00 

19.50 

16.50 

15.00 

13.50 

0.738 

0.747 

0.715(0.726 

0.733 

0.743 

0.748 

0.754 

0.691 

0.701 

0.708 

0.717 

Table  IV.    Spindle  Revolution  and  Cam  Rise  for  Threading 


Length  of 
Threaded 
Portion 

Number  of  Threads  per  Inch 

64 

56 

48 

40 

36 

32 

3° 

28 

24 

20 

18    |    16 

First  Line:  Revolutions  of  Spindle  for  Threading 
Second  Line:  Rise  on  Cam  for  Threading 

H 

54.50 
0.767 

48.50 
0.779 

40.50 
0.742 

34.50 
0.759 

31.00 
0.758 

28.00 
0.770 

26.50 
0.777 

25.00 
0.786 

20.50 
0.726 

17.00 
0.723 

15.50 
0.732 

14.00 
0.743 

11 

56.50 
0.795 

50.00 
0.804 

42.00 
0.770 

35.50 
0.781 

32.50 
0.794 

29.00 
0.798 

27.50 
0.807 

26.00 
0.817 

21.00 
0.744 

18.00 
0.765 

16.00 
0.755 

14.50 
0.770 

tt 

58.50 
0.823 

52.00 
0.836 

43.50 
0.797 

37.00 
0.814 

33.50 
0.819 

30.00 
0.825 

28.50 
0.836 

26.50 
0.833 

22.00 
0.779 

18.50 
0.786 

16.50 
0.779 

15.00 
0.797 

t 
j 

60.50 
0.851 

53.50 
0.860 

45.00 
0.825 

38.00 
0.836 

34.50 
0.843 

31.00 
0.853 

29.50 
0.865 

27.50 
0.864 

22.50 
0.797 

19.00 
0.808 

17.50 
0.826 

15.50 
0.823 

If 

62.50 
0.879 

55.50 
0.892 

46.50 
0.842 

39.50 
0.869 

35.50 
0.868 

32.00 
0.880 

30.00 
0.880 

28.50 
0.895 

23.50 
0.832 

19.50 
0.829 

18.00 
0.850 

16.00 
0.850 

H 

64.50 
0.907 

57.00 
0.916 

48.00 
0.880 

40.50 
0.891 

37.00 
0.904 

33.00 
0.908 

31.00 
0.909 

29.50 
0.927 

24.00 
0.850 

20.50 
0.871 

18.50 
0.873 

16.50 
0.876 

H 

66.50 
0.935 

59.00 
0.948 

49.50 
0.907 

42.00 
0.924 

38.00 
0.929 

34.00 
0.935 

32.00 
0.939 

30.00 
0.943 

25.00 
0.885 

21.00 
0.893 

19.00 
0.897 

17.00 
0.903 

i 

68.50 
0.963 

60.50 
0.972 

51.00 
0.918 

43.00 
0.946 

39.00 
0.953 

35.00 
0.963 

33.00 
0.968 

31.00 
0.974 

25.50 
0.903 

21.50 
0.914 

19.50 
0.920 

17.50 
0.929 

iA 

H 

72.50 
1.019 
76.50 
1.076 

64.00 
1.028 
67.50 
1.084 

54.00 
0.990 
57.00 
1.045 

45.50 
1.001 
48.00 
1.056 

41.50 
1.013 
43.50 
1.061 

37.00 
1.018 
39.00 
1.073 

35.00 
1.026 
37.00 
1.084 

32.00 
1.005 
34.50 
1.083 

27.00 
0.956 
28.50 
1.009 

23.00 
0.978 
24.00 
1.020 

20.50 
0.968 
22.00 
1.038 

18.50 
0.982 
19.50 
1.035 

1A 

80.50 
1.126 

71.00 
1.141 

60.00 
1.100 

50.50 
1.111 

46.00 
1.122 

41.00 
1.128 

38.50 
1.128 

36.50 
1.146 

30.00 
1.062 

25.50 
1.084 

23.00 
1.086 

20.50 
1.089 

li 

84.50 
1.188 

74.50 
1.197 

63.00 
1.155 

53.00 
1.166 

48.00 
1.171 

43.00 
1.183 

40.50 
1.187 

38.00 
1.193 

31.50 
1.115 

26.50 
1.126 

24.00 
1.133 

21.50 
1.142 

1T6* 

88.50 
1.244 

78.00 
1.253 

66.00 
1.210 

55.50 
1.221 

50.50 
1.232 

45.00 
1.238 

42.50 
1.245 

40.00 
1.256 

33.00 
1.168 

28.00 
1.190 

25.00 
1.180 

22.50 
1.195 

H 

92.50 
1.301 

81.50 
1.310 

69.00 
1.265 

58.00 
1.276 

52.50 
1.281 

47.00 
1.293 

44.50 
1.304 

41.50 
1.303 

34.50 
1.211 

29.00 
1.233 

26.50 
1.251 

23.50 
1.248 

1A 

96.50 
1.357 

85.00 
1.366 

72.00 
1.320 

60.50 
1.331 

55.00 
1.342 

49.00 
1.348 

46.00 
1.348 

43.50 
1.366 

36.00 
1.274 

30.50 
1.296 

27.50 
1.298 

24.50 
1.301 

H 

100.5 
1.413 

88.50 
1.422 

75.00 
1.375 

63.00 
1.386 

57.00 
1.391 

51.00 
1.403 

48.00 
1.406 

45.00 
1.413 

37.50 
1.328 

31.50 
1.339 

28.50 
1.345 

25.50 
1.354 

1A 
11 

Hi 

104.5 
1.469 

92.00 
1.478 
95.50 
1.535 
99.00 
1.591 

78.00 
1.430 
81.00 
1.485 
84.00 
1.540 

65.50 
1.441 
68.00 
1.496 
70.50 
1.551 

59.50 
1.452 
61.50 
1.501 
64.00 
1.562 

53.00 
1.458 
55.00 
1.513 
57.00 
1.568 

50.00 
1.465 
52.00 
1.524 
53.50 
1.568 

47.00 
1.476 
48.50 
1.523 
50.50 
1.586 

39.00 
1.381 
40.50 
1.434 
42.00 
1.487 

33.00 
1.403 
34.00 
1.445 
35.50 
1.509 

29.50 
1.392 
31.00 
1.463 
32.00 
1.510 

26.50 
1.407 
27.50 
1.460 
28.50 
1.513 



U 

102.5 
1.647 

87.00 
1.595 

73.00 
1.606 

66.00 
1.610 

59.00 
1.623 

55.50 
1.626 

52.00 
1.633 

43.50 
1.540 

36.50 
1.551 

33.00 
1.558 

29.50 
1.566 

HI 
U 

106.0 
1.703 

90.00 
1.650 
93.00 
1.705 

75.50 
1.661 
78.00 
1.716 

68.50 
1.671 
70.50 
1.720 

61.00 
1.678 
63.00 
1.733 

57.50 
1.685 
59.50 
1.743 

54.00 
1.696 
55.50 
1.743 

45.00 
1.593 
46.50 
1.646 

38.00 
1.615 
39.00 
1.658 

34.00 
1.605 
35.50 
1.676 

30.50 
1.620 
31.50 
1.673 





l« 

2 





96.00 
1.760 
99.00 
1.815 

80.50 
1.771 
83.00 
1.826 

73.00 
1.781 
75.00 
1.830 

65.00 
1.788 
67.00 
1.843 

61.00 
1.787 
63.00 
1.846 

57.50 
1.806 
59.00 
1.853 

48.00 
1.700 
49.50 
1.752 

40.50 
1.721 
41.50 
1.764 

36.50 
1.723 
37.50 
1.770 

32.50 
1.726 
33.50 
1.779 

ALLOWANCE  FOR  TOOL  CLEARANCE 


247 


center  and  radius  OE,  join  points  b  and  a ;  with  e  as  a  center 
and  radius  OE,  join  points  c  and  a.  This  gives  the  shape  of 
the  thread  lobe. 

For  convenience  in  cutting,  when  a  Brown  &  Sharpe  circu- 
lar milling  attachment  is  available,  the  cam  surface  used  for 
threading  is  divided  into  minutes.  Then,  to  obtain  the  lead 
(or  the  number  of  minutes  traversed  for  each  y  oW-hich  rise) 
divide  the  number  of  minutes  contained  in  the  portion  of  the 
lobe  used,  by  the  rise.  For  example,  0.810  -r-  0.413  =  1.96, 
or  2  minutes,  approximately. 

Allowance  for  Tool  Clearance.  —  In  laying  out  a  set  of 
cams,  it  is  sometimes  found  necessary  to  make  allowance 


FACE  OF  DIE  HOLDER 


CUT-OFF  TOOL-\ 


JL 


J^TOOL  POST 
VFORM  TOOL 


V 

XFACE  OF  DIE  HOLDER 


MacMnery,N.Y. 


Fig.  9.   Diagram  illustrating  Method  of  Finding  Clearance  for  Die-holder 

for  one  tool  to  clear  another,  the  amount  of  clearance  neces- 
sary being  determined  by  the  diameter  or  width  of  tool  used 
in  the  turret  and  the  position  of  the  cross-slide  tools  relative 
to  the  work.  When  determining  the  amount  of  clearance 
necessary,  the  rise  and  drop  on  the  lead  cam  is  disregarded 
and  the  rises  and  drops  on  the  front-slide  and  back-slide 
cams  are  taken  into  consideration.  To  determine  the  rise  and 
drop  to  use,  make  a  rough  lay-out  of  the  various  operations 
to  be  performed  and  also  ascertain  the  approximate  number 
of  revolutions  to  complete  one  piece.  The  revolutions  are 
then  converted  into  seconds.  Assume  that  it  is  required  to 
make  a  brass  screw  as  shown  in  Fig.  9.  This  screw  is  to  be 
made  from  J-inch  round  brass  rod,  on  the  No.  oo  Brown  & 


248 


CAM  DESIGN 


Sharpe  automatic  screw  machine,  using  a  spindle  speed  of 
2400  revolutions  per  minute  backward  and  forward.  Assume 
that  it  is  required  to  find  the  amount  of  clearance  necessary 
for  the  die-holder  to  pass  the  circular  form  and  cut-off  tools. 
Draw  in  the  form  tool  in  position  on  the  screw  as  shown  to  the 
left,  and  also  an  outline  of  the  toolpost.  Then  lay  out  the  die- 
holder  in  position  to  start  on  the  screw,  as  shown  by  the  dotted 


Machinery,  N.Y. 


Fig.  10.   Method  of  Determining  Clearance  on  Cross-slide  Cams 

lines.  If  a  releasing  die-holder  is  used,  take  the  diameter  over 
the  heads  of  the  screws  in  the  holder,  but,  if  a  "draw-out" 
type  is  used,  the  diameter  of  the  cap  is  taken.  In  this  case, 
assume  that  a  releasing  die-holder  is  to  be  used.  The  die- 
holder  cannot  advance  on  the  screw  until  the  form  tool  drops 
back  a  distance  B,  but,  as  B  is  the  actual  distance,  it  will  be 
necessary  to  add  an  extra  amount  to  insure  that  the  die-holder 
can  advance  without  coming  in  contact  with  the  circular  form 


ALLOWANCE  FOR  TOOL  CLEARANCE        249 

tool.  The  extra  amount  of  clearance  necessary  varies  with 
the  type  of  tool  used.  The  following  dimensions  give  the 
approximate  amounts  that  should  be  added  to  the  actual 
clearance  for  the  type  of  tools  specified : 

Extra  Amount 

Type  of  Tool  of  Clearance, 

Inch 

Drill-holders from    |  to  -fa 

Box-tools  (with  V-supports) from    f  to    £ 

Box-tools  (with  supporting  bushing) from  -^  to  T\ 

Button-die  holders  (draw-out  type) from  T\  to  T\ 

Button-die  holders  (releasing  type) from    |  to    5 

To  find  the  amount  necessary  for  clearance,  make  a  diagram 
as  shown  in  Fig.  10,  laying  out  the  drop  on  the  front  cam  as 
shown.  Then  add,  say,  J  inch  to  dimension  B  and  measure 
down  from  the  point  where  the  lobe  finishes,  scribing  an;  arc 
of  a  circle  through  the  point  thus  located,  as  shown.  Then 
with  a  radius  equal  to  the  radius  of  the  cam  roll,  describe  a 
circle  touching  the  arc  drawn  and  the  drop  on  the  cam.  Join 
the  center  of  the  roll  with  the  center  of  the  cam  circle  by  a 
straight  line.  The  clearance  is  then  measured  off  in  hundred ths, 
as  shown  by  dimension  H.  The  starting  point  of  the  lobe  on 
the  lead  cam  for  threading,  will  be  at  the  hundredth  line  D, 
and  the  intervening  space  between  the  lines  D  and  E  will  be 
the  amount  necessary  for  clearance. 

When  the  cutting-off  operation  follows  the  threading  opera- 
tion, it  will  also  be  necessary  to  allow  for  clearance.  To  find 
the  amount  of  clearance  necessary  for  the  die-holder  to  clear 
the  circular  cut-off  tool,  proceed  as  follows :  Make  a  lay-out 
as  shown  to  the  right  in  Fig.  9,  measure  the  distance  C,  add 
J  inch  to  C,  and  lay  off  this  dimension  from  the  starting  point 
A  of  the  rear  cam  as  shown  in  Fig.  10,  drawing  an  arc  of  a 
circle  as  before.  Then  draw  a  circle  the  diameter  of  which  is 
equal  to  the  diameter  of  the  roll,  touching  the  arc  drawn 
and  the  rise  on  the  cam,  and  measure  off  the  clearance  H  as 
previously  explained.  The  thread  lobe  would  finish  at  the 
hundredth  line  F  and  the  cut-off  tool  start  at  the  line  A. 
Clearance  should  also  be  allowed  between  the  dropping  back 
of  the  cut-off  tool  and  the  feeding  of  the  stock.  To  find  the 


25° 


CAM   DESIGN 


amount  of  clearance  necessary  add  J  inch  to  the  largest  radius 
of  the  stock  used,  and  proceed  as  previously  explained. 

Use  of  Cam-lever  Templets.  —  Cam-lever  templets  similar 
to  those  shown  in  Fig.  n  are  used  for  laying  out  cams  when 
very  close  timing  is  required,  as,  for  instance,  when  a  tool 
is  operated  by  the  combined  action  of  the  cross-slide  and  the 
turret-slide.  When  templets  are  used,  the  center  A  is  pivoted 
at  the  center  of  the  cam  drawing,  by  inserting  a  pin  or  other 
pointed  instrument  through  the  small  hole  provided  for  that 


CENTER  OF  FULCRUM 

OF  CROSS-SLIDE 

CAM  LEVER 


CAM  LEVER  TEMPLETS 
FOR  NO3. 1  &.2.  B.  &S.  AUTO.  S. 


CAM  LEVER  TEMPLETS  ^T      CAM  LEVER  TEMPLETS 
FOR  NO.O.B.4S.AUTO.S.M.    A    FOR  NO.  00.  B.  4S.  AUTO.  S.  M. 


Fig.  11.  Nos.  00,  0, 1,  and  2,  Brown  &  Sharpe  Automatic  Screw  Machine 
Cam-lever  Templets  for  Finding  the  Starting  and  Finishing  Points 
of  the  Lobes  for  the  Cross-slide  and  Lead  Cams 

purpose.  The  main  body  B  of  the  templet  can  then  be  rotated 
in  any  desired  direction,  so  that  the  two  templet  arms,  repre- 
senting the  cross-slide  cam  lever  and  the  lead  cam  lever  which 
operates  the  turret,  can  be  set  in  whatever  position  relative 
to  each  other  may  be  required.  These  cam-lever  templets  are 
made  from  sheet  celluloid  and  are  transparent,  so  that  marks 
on  the  drawing  can  easily  be  seen.  The  use  of  a  cam-lever 
templet  will  be  illustrated  by  considering  the  method  of  find- 
ing the  starting  and  finishing  points  on  the  lobes  of  the  cross- 
slide  and  lead  cams  for  a  chamfering  operation. 

There  are  two  methods  used  in  laying  out  a  set  of  cams 
when  it  is  necessary  to  obtain  clearances  or  definite  starting 


CAM-LEVER   TEMPLETS 


251 


points  for  the  lead  and  cross-slide  cam  lobes.  The  first  one  is 
to  obtain  a  rough  estimate  of  the  total  number  of  revolutions 
required  to  complete  one  piece,  after  which  the  revolutions 
are  transferred  into  hundredths  of  cam  circumference,  and  the 
location  of  the  lobes  laid  out  on  the  cam  circles.  Then  the 
"rises"  and  " drops"  are  constructed  and  the  amount  of  clear- 
ance obtained  by  the  cam-lever  templets.  This  method  usually 
requires  considerable  experience  in  this  line  of  work. 

Another  method  is  to  first  find  the  rise  on  the  cross-slide  cam 
for  chamfering.     Then  draw  a  diagram  as  shown  in  Fig.  12. 


CENTER  OF  FULCRUM  OF  CROSS^SLIDE  LEVER 


Fig.  12.   Diagram  for  Finding  the  Starting  and  Finishing  Points  of  the 
Lobes  of  the  Cross-slide  and  Lead  Cams  for  Chamfering  Operations 

First  draw  circles  L  and  S,  representing  the  largest  diameter 
of  the  lead  cam  and  the  largest  diameter  of  the  cross-slide  cam, 
respectively;  then  draw  another  circle  H  a  distance  R  inside 
of  the  circle  S,  as  shown,  the  dimension  R  being  the  rise  on 
the  cross-slide  cam.  In  chamfering  operations,  the  tool  should 
move  longitudinally  the  proper  distance  into  the  work  before 
the  cross-slide  cam  starts  to  operate.  Therefore,  the  lead- 
cam  roll  should  be  on  the  highest  point  of  the  lobe  before  the 
cam  on  the  cross-slide,  used  for  feeding  in  the  tool,  touches 
the  tool-holder.  In  order  to  accomplish  this  result,  proceed 
as  follows.  Draw  a  circle  G,  as  shown  in  Fig.  12,  which  has  a 
radius  an  amount  R  -f-  D  -f-  yV  smaller  than  that  of  circle  S. 


252  CAM  DESIGN 

The  value  of  D  is  equal  to  the  distance  that  the  point  of  the 
tool  extends  in  from  the  face  of  the  work  when  in  position  for 
chamfering.  The  •£$  inch  added  to  D  allows  for  clearance. 
After  these  circles  have  been  drawn,  the  starting  and  finishing 
points  of  the  lobes  can  be  found. 

The  cam-lever  templet  is  now  placed  in  position,  and  the 
lead-cam  roll  is  located  so  that  its  circumference  touches  the 
lobe  on  the  lead  cam  and  its  center  coincides  with  the  line 
A  indicating  the  completion  of  the  lead-cam  rise.  Then  the 
cross-slide  lever  is  swung  down  so  that  the  circumference  of 
the  roll  touches  the  circle  G  as  shown,  and,  with  a  sharp  pencil, 
a  line  is  scribed  around  the  circumference  of  the  roll,  which 
will  determine  the  quick  rise  of  the  cam.  The  compasses  are 
then  set  to  the  desired  radius  for  the  quick  rise  of  the  cam,  which 
is  described  so  that  it  will  cut  the  circle  #,  representing  the 
start  of  the  rise  on  the  cross-slide  cam,  and  also  be  tangent  to 
the  line  which  has  been  previously  marked  by  scribing  around 
the  cross-slide  lever  roll.  Where  the  quick  rise  of  the  cam 
and  the  circle  H  meet  will  be  the  starting  point  of  the  rise 
on  the  cross-slide  cam,  indicated  by  the  line  J3,  as  shown. 

When  the  starting  points  have  been  found,  the  next  thing 
is  to  obtain  the  finishing  points  of  the  lobe.  The  lead  cam 
should  hold  the  tool  in  position  until  the  cross-slide  cam  has 
dropped  back  an  amount  equal  to  the  distance  which  it  has 
fed  the  tool  into  the  work.  A  line  F  is  drawn  at  any  con- 
venient position  for  the  finishing  point  of  the  lead  cam,  and  the 
cam-lever  templet  is  then  brought  into  position  so  that  the 
roll  of  the  lead  lever  touches  the  circle  and  the  center  coin- 
cides with  the  line  F  as  shown.  The  cross-slide  roll  is  then 
swung  down  until  its  circumference  touches  the  circle  H  and 
a  line  is  scribed  around  the  circumference  of  the  roll.  Where 
this  line  intersects,  the  circle  representing  the  largest  diameter 
of  the  cam  will  be  the  finishing  point  of  the  lobe,  provided  the 
distance  R  is  not  greater  than  the  radius  of  the  roll.  If  distance 
R  is  greater  than  this  radius,  the  line  representing  the  drop 
should  be  constructed  tangent  to  the  roll  circumference,  and 
where  the  line  representing  the  drop  intersects  the  outside 


CAM-LEVER  TEMPLETS 


253 


circle  will  be  the  finishing  point  of  the  lobe,  as  indicated  by 
line  C.  The  space  from  E  to  C  represents  from  one  to  two 
revolutions  for  dwell  on  the  cross-slide  cam.  The  advantage 
of  this  method  is  that  the  amount  of  clearance  between  the 
starting  and  finishing  points  of  the  lead  and  cross-slide  cams 
is  known  in  hundredths  of  the  cam  circle  circumference  before 
the  cams  are  laid  out,  thus  facilitating  the  operation  of  laying 
out  the  cams. 

Laying  Out  Cams  for  Recessing.  —  In  Fig.  13  a  method  is 
shown  for  finding  the  starting  and  finishing  points  on  the 


CENTER  OF  FULCRUM  OF  LEAD  LEVER 


Fig.  13.   Diagram  for  Finding  the  Starting  and  Finishing  Points  on  the 
Lobes  of  the  Cross-slide  and  Lead  Cams  for  Recessing  Operations 

lobes  of  the  cross-slide  and  lead  cams  for  recessing.  To  deter- 
mine these  points,  the  cam-lever  templets  are  used.  The 
starting  point,  indicated  by  line  A,  and  the  circle  represent- 
ing the  dwell  on  the  lead  cam  are  first  laid  out.  A  circle  is 
then  drawn,  the  radius  of  which  is  a  distance  K  greater  than 
the  circle  representing  the  dwell  on  the  lead  cam.  (Distance 
K  is  equal  to  the  length  of  the  recessing  cut.)  Before  begin- 
ning to  lay  out  the  cam,  a  maximum  cam  diameter  should  be 
decided  upon  which  will  suit  the  length  of  the  tool-holder  used 
in  the  turret.  A  circle  passing  through  the  starting  point  of 
the  rise  of  the  cross-slide  cam,  as  well  as  a  circle  representing 
the  dwell  on  the  cross-slide  cam,  should  also  be  drawn,  the 


254 


CAM  DESIGN 


difference  in  radii  between  these  two  circles  being  the  rise  R. 
Now  the  cam-lever  templets  are  placed  in  position  on  the 
drawing,  and  the  lead  roll  brought  down  so  that  it  touches  the 
lead  cam,  its  center  coinciding  with  line  A.  A  circle  M  is  next 
drawn,  having  a  radius  L  +  yV  mcn  less  than  that  of  the  circle 
passing  through  the  starting  point  of  the  rise  of  the  cross- 
slide  cam.  L  equals  the  distance  from  the  outer  face  of  the 
work  to  the  inner  edge  of  the  recessing  tool  when  the  latter  is 
in  the  starting  position.  The  cross-slide  roll  is  then  swung 
down  until  its  circumference  touches  the  circle  M,  as  shown, 
and  a  line  is  drawn  around  the  circumference  of  the  roll.  The 


kl— E — H 
H  h~  c— i  I 


FULCRUM  OF  RECESSING  HOLDER/ 
POINT  OF  APPLICATION  OF  CAM 


Machinery,  N.  y. 


Fig.  14.   Diagram  for  Finding  Rise  on  Cross-slide  Cam  for  Recessing 
and  Chamfering  Operations 

quick  rise  line  of  the  cam  is  then  constructed  tangent  to  the 
roll,  and  where  this  line  intersects  the  circle  previously  drawn, 
which  determines  the  beginning  of  the  slow  feeding-in  rise  of 
the  cross-slide  cam,  is  the  starting  point  of  the  slower  rise  of 
the  cross-slide  cam,  as  shown  at  B.  The  line  C,  which  repre- 
sents the  finishing  point  of  the  rise  on  the  cross-slide  cam  for 
feeding  the  tool  inward,  is  then  laid  off  and  the  cross-slide  roll 
swung  into  position.  The  lead  roll  is  then  swung  down  until 
it  touches  the  circle  representing  the  dwell  on  the  lead  cam. 
The  starting  point  of  the  rise  on  the  lead  cam,  located  on  line 
Dj  is  slightly  in  advance  of  the  finishing  point  on  the  cross- 
slide  cam. 

The  finishing  points  of  the  lobes  are  next  located.    Any  line, 
as  Gj  is  taken  at  a  convenient  location,  and  the  cam-lever 


CAM  FOR  RECESSING  AND   CHAMFERING  255 

templets  are  then  used.  The  lead  roll  is  first  brought  into 
position  as  shown,  and  then  the  cross-slide  roll  is  swung  down 
from  the  outside  diameter  of  the  cam  a  distance  equal  to 
R,  and  the  drop  laid  off  as  before  mentioned  in  regard  to  cham- 
fering operations.  The  finishing  point  of  the  cross-slide  lobe 
would  then  be  on  the  line  E.  The  space  from  C  to  E  on  the 
cross-slide  cam  would  be  for  dwell,  while  the  space  from  D 
to  G  on  the  lead  cam  would  be  the  rise.  The  space  from  F 
to  G  is  for  dwell  on  the  lead  cam,  which  represents  about  one 
or  two  revolutions. 

Rise  on  Cross-slide  Cam  for  Recessing  and  Chamfering.  — 
When  using  a  swing  tool  for  recessing,  the  rise  on  the  cam 
should  be  greater  than  the  distance  which  the  tool  is  fed  into 
the  work.  To  illustrate  the  method  of  finding  the  rise  on  the 
cam,  refer  to  Fig.  14,  where 

A  =  distance  from  center  of  fulcrum  to  center  of  the  recessing 
tool; 

B  =  distance  from  center  of  fulcrum  to  point  of  application 
of  cam  or  center  of  screw  at  end  of  swinging  member; 

C  =  diameter  of  recessing  tool ; 

D  =  diameter  of  drilled  hole  in  the  work ; 

E  =  diameter  of  recessed  hole ; 

E-C 
r  =  travel  of  recessing  tool  =  ; 

R  =  rise  on  the  cam. 

Then  R:r::B:A.  As  a  practical  example,  let  r  equal 
0.040  inch;  B,  i\  inches;  A,  i|  inch;  then 

0.040  X  2j  . 

R  =  -  —  =  0.080  inch. 

if 

Cam  Rise  for  Drilling.  —  There  are  three  general  conditions 
which  govern  the  amount  of  rise  required  for  drilling:  i. 
When  the  drill  does  not  pass  through  the  work  and  a  center- 
ing tool  is  not  used.  2.  When  the  drill  does  not  pass  through 
the  work  and  a  centering  tool  is  used.  3.  When  the  drill  passes 
through  the  work  and  a  centering  tool  is  used.  There  is  also 
another  condition,  viz.,  when  the  drill  passes  through  the  work 


256 


CAM  DESIGN 


and  a  centering  tool  is  not  used;    but,  as  this  is  not  a  com- 
mendable method,  it  is  not  here  considered. 

The  rise  on  the  cam  for  drilling,  as  governed  by  the  previous 
conditions,  is  as  follows : 

1.  R  =  g  +  e+  o.oio  inch; 

2.  R  =  g  —  a  +  o.oio  inch ; 

3.  R=  h  +  k  —  a+  o.oio  inch ; 


1C  "TO   »   DEPENDING 
ON  DEPTH  OF  HOLE  AND  \J 
DIAMETER  OF  DRILL 


Fig.  15.   Method  of  Laying  Out  Cams  for  Deep-hole  Drilling 

where  R  =  rise  on  cam  for  drilling ; 

g  =  depth  of  hole  to  be  drilled ; 
e  =  length  of  point  on  the  drill ; 
h  =  overall  length  of  the  work ; 
k  =  thickness  of  the  cut-off  tool ; 

a  =  distance  from  the  face  of  the  work  to  a  place  in 
the  centered  end  where  the  outer  edges  of  the 
drill  begin  to  cut. 

The  values  of  a  for  centering  tools  having  90-  and  100- 
degree-point  angles  are  as  follows : 

For    90  degrees,  a  =  (d  —  c)  X  0.5    inch ; 
For  100  degrees,  a  =  (d  —  c)  X  0.43  inch ; 
where  d  =  diameter  of  centering  hole ; 
c  —  diameter  of  drill. 


CAM  FOR  DEEP-HOLE   DRILLING  257 

Designing  Cams  for  Deep-hole  Drilling.  —  When  drilling 
deep  holes,  the  drill  should  be  withdrawn  clear  of  the  drilled 
hole,  after  penetrating  to  a  depth  not  exceeding  two  and  one- 
half  times  the  drill  diameter,  so  that  the  chips  can  be  removed 
from  the  flutes  and  the  drill  cooled  and  lubricated.  To  ac- 
complish this,  the  lead  cam  is  laid  out  as  shown  in  Fig.  15.  To 
explain  the  method  used  for  laying  out  the  cam,  assume  that 
a  hole  f  inch  in  diameter  and  f  inch  long  is  to  be  drilled  in  a 
piece  of  brass  rod.  This  will  require  three  lobes  on  the  cam, 
as  it  will  be  necessary  to  drop  the  drill  back  twice  in  producing 
the  hole.  The  rises  for  the  various  lobes  can  be  found  with 
the  aid  of  the  following  formulas  : 

Rise  on  first  lobe      =  i\  X  D  +  0.005  ^ncn  J 

Rise  on  second  lobe  =  2|  X  D  +  0.003  inch ; 

Rise  on  third  lobe     =  2    X  D  +  0.003  inch ; 
where  D  =  diameter  of  drill  in  inches. 

The  amount  for  each  successive  rise  should  be  decreased  in 
about  the  same  proportion,  and  the  feed  on  the  drill  should 
also  be  decreased  slightly  for  each  additional  lobe  when  cutting 
machine  and  tool  steel ;  but,  when  cutting  brass,  the  feed  can 
generally  be  uniform  for  each  lobe.  The  rise  on  the  various 
lobes  would  then  be  as  follows : 

Rise  on  first  lobe      =  2f  X  J  +  0.005  =  °-349  inch ; 

Rise  on  second  lobe  =  2§  X  J  +  0.003  =  0.300  inch ; 

Rise  on  third  lobe     =2    X  f  +  0.003  =  0.253  inch. 

The  depth  to  which  the  drill  can  be  fed  into  the  work  before 
withdrawing  can  sometimes  be  increased,  especially  when  a 
turret  drilling  attachment  is  used  and  the  drill  is  greater  than 
J  inch  in  diameter.  The  space  on  the  cam  surface  necessary 
for  dropping  the  drill  back  is  generally  equal  to  the  space 
necessary  for  revolving  the  turret.  It  is,  therefore,  advisable 
to  use  more  than  one  drill  when  there  is  a  sufficient  number 
of  empty  holes  in  the  turret,  as  it  will  not  be  necessary  to 
resharpen  the  drills  so  frequently,  and  they  will  also  be  kept 
cooler. 


CHAPTER  VIII 

OPERATIONS    ON   SINGLE-   AND    MULTIPLE-SPINDLE 
SCREW    MACHINES 

THE  operations  ordinarily  performed  in  automatic  screw 
machines  involve  plain  cylindrical  turning,  taper  turning, 
forming  of  irregular  surfaces,  drilling,  counterboring,  reaming, 
cutting  annular  grooves  or  recesses  in  holes,  thread  cutting, 
and  knurling.  The  number  and  kind  of  cutting  tools  used  on 
the  machines  depend,  of  course,  upon  the  nature  of  the  work ; 
that  is,  its  size  and  the  form  and  location  of  the  surfaces  which 
must  be  acted  upon  by  the  tools.  The  turning  of  simple  parts, 
such  as  ordinary  screws,  pins,  etc.,  from  a  bar  of  stock  can  be 
done  by  using  the  regular  tool  equipment  commonly  em- 
ployed on  all  screw  machines,  whereas  more  difficult  work 
might  necessitate  the  use  of  special  tools  and,  in  some  cases, 
attachments  for  extending  the  range  of  the  machine.  Before 
a  machine  of  this  type  is  equipped  for  a  machining  operation, 
it  is  essential  to  consider  the  best  method  of  arranging  the 
various  tools,  as  well  as  the  different  types  of  tools  available, 
so  that  the  successive  operations  may  be  performed  to  the 
best  advantage  as  to  economy  of  production  and  the  degree 
of  finish  and  accuracy  required.  To  what  extent  standard 
tools  may  be  used  should  also  be  determined,  and  whether  or 
not  special  tool  equipment  will  increase  the  rate  of  production 
sufficiently  to  warrant  their  expense. 

A  general  idea  of  the  tool  equipment  used  for  different  opera- 
tions and  also  the  classes  of  work  for  which  automatic  screw 
machines  are  used  may  be  obtained  by  studying  the  examples 
described  in  this  chapter.  Some  of  these  examples  illustrate 
the  use  of  comparatively  simple  tool  equipment,  whereas  others 
represent  operations  for  which  special  tools  and  ingenious  at- 
tachments are  required. 

258 


POINTING  END   OF  WORK 


259 


Before  reducing  the  diameter  of  the  work  by  means  of  a 
box-tool  or  other  external  cutting  tool  of  a  similar  type,  it  is 
necessary  to  chamfer  the  end  of  the  work  to  permit  starting 
the  box-tool  cutter  on  a  light  cut,  until  the  supports  are  in 
position  to  steady  the  work.  Pointing  or  chamfering  the  end 
of  the  work  also  facilitates  the  setting  of  a  hollow  mill  concen- 
tric with  the  work. 

One  method  of  pointing  the  end  of  the  work  is  shown  at  A 
in  Fig.  i.  The  circular  cut-off  tool  has  an  angular  projection 
on  its  face  next  to  the  chuck,  which  points  the  bar  before  it 


URCULAR  CUT-OFF 
TOOL 


at  3       fe 


,CIRCULAR  FORM 
TOOL 


— J 


Fig.  1.   Methods  of  Preparing  Work  for  Turning 

is  fed  out  for  the  next  piece.  This  method  is  generally  used 
when  the  work  is  not  very  long,  and  when  it  runs  practically 
true.  When  it  is  necessary  to  cut  a  thread  on  a  piece,  the 
beveled  end  of  the  bar  is  made  small  enough  to  facilitate 
the  starting  of  the  die.  It  is  sometimes  impossible  to  point 
the  bar  with  the  cut-off  tool,  and,  in  this  case,  the  bar  is  usually 
pointed  by  a  combination  centering  and  pointing  tool  as  shown 
at  B.  This  tool  can  be  used  when  the  bar  does  not  project 
more  than  three  and  one-half  times  its  diameter  from  the 
face  of  the  chuck,  and  also  when  the  bar  is  unfinished  or  of 
irregular  shape.  The  tool  a  is  used  for  centering  the  work, 
thus  preparing  it  for  drilling  a  hole,  and  the  tool  b  is  used  for 
pointing  the  end  of  the  bar. 


260  SCREW  MACHINE  PRACTICE 

Another  condition  is  shown  at  C.  Here  the  form  tool  pre- 
cedes the  box-tool,  " necking"  the  bar  at  a.  If  the  face  b  of 
the  circular  tool  were  left  square  and  not  chamfered,  as  shown, 
a  thin  ring  would  break  off  before  all  the  material  had  been 
removed,  as  illustrated  at  Ca,  Fig.  2,  Chapter  IV. 

Turning  Concentric  with  Unturned  Surface.  —  When  it  is 
necessary  to  turn  down  a  portion  of  a  long  cylindrical  piece 
of  cold-drawn  steel  or  other  material  which  has  a  finished 
surface,  and  have  the  part  turned  concentric  with  that  which 
has  not  been  reduced,  it  is  usually  good  practice  to  weaken 
the  bar  with  the  circular  cut-off  tool  as  shown  at  D,  Fig.  i. 
For  this  class  of  work,  a  supporting  bushing  held  in  the  box- 
tool  should  precede  the  turning  tool,  so  that  the  part  turned 
will  be  concentric  with  the  finished  body  of  the  work.  Before 
turning,  the  bar  is  pointed  with  the  circular  cut-off  tool  as 
shown  at  A. 

The  diameter  a  of  the  neck  should  be  small  enough  to  allow 
the  bar  to  be  straightened  with  the  box-tool  support,  so  that 
it  will  run  true.  In  the  majority  of  cases,  the  neck  a  may  be 
made  from  0.3  to  0.5  times  5,  but  the  length  c  of  the  work, 
the  depth  of  the  chip  removed,  and  the  feed  used,  will  govern 
largely  the  diameter  of  the  neck.  The  material  being  turned 
will  also  affect  this  diameter  slightly,  but  in  most  cases  this 
latter  condition  can  be  disregarded.  Rods  which  have  short 
bends  in  them  should  not  be  used,  as  it  will  be  found  impos- 
sible to  produce  a  good  surface  on  the  part  which  is  turned. 
The  spring  collet  should  also  run  perfectly  true,  if  good  results 
are  to  be  expected. 

Examples  of  Forming  Operations.  —  According  to  a  common 
rule,  two  and  one-half  times  the  smallest  diameter  of  the 
work  is  the  maximum  width  advised  for  forming ;  that  is,  the 
width  of  the  form  tool  cutter  a  for  forming  the  screw  at  A  in 
Fig.  2  should  not  exceed  two  and  one-half  times  the  diameter 
of  the  threaded  body  b.  This  means  that,  when  a  piece  is  too 
long  to  form,  it  must  be  reduced  by  an  end- working  tool, 
such  as  a  hollow  mill  or  a  box-tool. 

This  rule,  however,  is  subject  to  variations.    By  actual  test 


FORMING  OPERATIONS 


261 


it  has  been  found  that  screws  and  other  parts  made  from 
machine  and  tool  steel  can  be  formed  with  a  form  tool  the 
width  of  which  is  four  times  the  smallest  diameter  of  the  part 
to  be  formed.  This  does  not  mean  a  piece  of  the  shape  shown 
at  B  in  Fig.  2,  where  the  smallest  diameter  c  is  on  the  end  of 


Fig.  2.   Examples  of  Forming  Tool  Operations 

the  piece,  but  it  applies  to  pieces  similar  to  those  shown  at 
A,  C,  and  D,  where  the  smallest  diameter  of  the  work  is  next 
to  the  spindle.  Again,  it  would  be  very  easy  to  form  with  a 
tool  of  a  width  equal  to  four  times  the  smallest  diameter,  if 
that  diameter  were  not  very  small.  Two  examples  of  this 


,-CIRCULAR  FORM 
^  TOOL 


CIRCULAR  CUT-OFF 


^-CIRCULAR 


FORM  TOOL 


CIRCULAR  CUT-OFF^ 


Machinery.  N.  Y. 


Fig.  3.   Method  of  Applying  the  Circular  Forming  and  Cutting-off  Tools 

class  of  forming  are  given,  and  can  safely  be  used  as  a  guide 
for  doing  work  of  a  similar  character. 

The  first  test  was  the  forming  of  a  f -inch  piece  of  screw  stock 
with  a  tool  ~IQ  inch  wide,  down  to  ^  inch  in  diameter.  In 
this  case,  the  width  is  four  times  the  smallest  diameter. 
This  test  was  performed  on  a  No.  2  Brown  &  Sharpe  automatic 


262  SCREW  MACHINE  PRACTICE 

screw  machine  and  the  surface  speed  of  the  stock  averaged 
about  from  80  to  85  feet  per  minute,  with  a  feed  of  o.ooi  inch 
per  revolution.  This  forming  was  successfully  done  without 
any  of  the  pieces  breaking  off.  The  second  test  was  made  on 
a  piece  of  |-inch  iron  wire,  which  was  formed  to  a  diameter 
of  -IQ  inch,  the  form  tool  in  this  case  being  i  inch  wide.  This 
test  was  made  on  a  |-inch  Cleveland  automatic  screw  machine. 
The  maximum  surface  speed  of  the  stock  was  90  feet  per  min- 
ute and  it  was  calculated  as  nearly  as  possible  that  the  chip 
averaged  from  0.0004  to  0.0008  inch  thick.  Therefore,  the  use 
of  a  hollow  mill  or  box-tool  can  sometimes  be  avoided  and 
circular  form  and  cut-off  tools  used  instead.  The  two  methods 
of  forming  the  piece  shown  at  A  and  B  in  Fig.  3  on  the  No.  2 
Brown  &  Sharpe  automatic  screw  machine,  and  the  following 
order  of  operations,  show  clearly  the  advantage  that  the  form- 
ing method  has  over  the  box-tool  or  hollow-mill  method  of 
turning.  With  the  method  shown  at  A,  two  roughing  box- 
tools  are  used  for  reducing  the  diameter  of  the  stem  6,  and, 
as  the  stem  was  also  required  to  be  smooth,  a  finishing  box-tool 
was  used,  as  can  be  seen  in  the  following  order  of  operations. 
The  feed  also  had  to  be  fine,  to  avoid  a  large  teat,  as  the  cut-off 
tool  forming  such  a  round  head  would  cause  the  piece  to  break 
off  before  it  had  been  entirely  cut  off. 

Revo-  Hun- 
Order  of  Operations  lutions  dredths 

Feed  stock  to  stop 29  2 

Revolve  turret 29  2 

First  roughing  box-tool  —  o.soo-inch  rise  at  o.oos-inch  feed. .  100  8 

Revolve  turret 29  2 

Second  roughing  box-tool  —  o.5oo-inch  rise  at  o.oo5-inch  feed  100  8 

Revolve  turret 29  2 

Finishing  box-tool  —  o^oo-inch  rise  at  o.oo5-inch  feed 100  8 

Revolve  turret ^ 29  2 

Form  —  o.5io-inch  rise  at  o.ooi5-inch  feed 340  29 

Cut-off  —  o.332-inch  rise  at  o.ooo9-inch  feed 383  33 

Revolve  turret  twice  while  cutting  off (58)  (5) 

Total  number  of  revolutions  to  make  one  piece 1168  100 

The  spindle  speed  used  was  549  revolutions  per  minute,  so 
that  the  time  to  make  one  piece  was  135  seconds,  gross  product 
in  ten  hours,  266  pieces.  The  new  method  of  making  this  piece 
is  shown  at  B  in  Fig.  3.  The  form  tool  travels  the  same  dis- 


FORMING  OPERATIONS 


263 


tance  as  when  using  the  method  shown  at  A,  but  a  much  finer 
feed  is  employed  on  account  of  the  greater  width  of  the  form 
tool.  No  time  is  lost,  however,  as  one  piece  is  being  cut  off 
at  the  same  time  that  another  piece  is  being  formed.  It  might 
be  well  to  mention  that  no  trouble  was  experienced  by  feeding 


Fig.  4.   Cams  for  Making  the  Piece  shown  in  Fig.  3  by  the  Method 
shown  at  B 

the  stem  out  against  the  stop ;  that  is,  the  stem  b  did  not  bend 
or  become  distorted  in  any  way. 

By  comparing  the  following  order  of  operations  with  those 
previously  given,  it  will  be  noticed  that  there  is  considerable 
increase  in  production,  and  also  that  the  work  is  handled 
more  expeditiously. 

Revo- 
Order  of  Operations  lutions 

Feed  stock  to  stop 16 

Cut-off  —  0.33  2-inch  rise  at  o.oooy-inch  feed 503 

Form  —  0.5 lo-inch  rise  at  o.ooi-inch  feed (503) 

Revolve  turret  five  times (go) 

Total  number  of  revolutions  to  make  one  piece 519 


Hun- 
dredths 

3 

97 
(97) 


264 


SCREW  MACHINE  PRACTICE 


The  speed  of  the  spindle  was  519  revolutions  per  minute, 
giving  a  maximum  surface  speed  of  84  feet  per  minute.  The 
time  required  to  make  one  piece  was  60  seconds,  giving  a  gross 
product  of  600  pieces  in  ten  hours.  This  is  a  considerable 
increase  as  compared  with  the  266  pieces  obtained  by  the 
method  shown  at  A,  and  the  gain  is  not  made  by  " hogging" 
out  the  work,  because  the  feeds  are  finer  and  the  work  is  better. 

The  cams  used  for  the  operation  shown  at  B  in  Fig.  3  are 
shown  in  Fig.  4.  The  cut-off  and  form  cams  start  at  o  hun- 
dredths  and  finish  at  97  hundredths  on  the  cam  circle.  The 


'Machinery 


Fig.  5.  Piece  to  be  Made  —  Arrangement  of  the  Circular  Tools 

form  cam  is  shown  by  the  dotted  lines  and  the  cut-off  by  long 
dashes ;  and  the  lead  cam  by  a  full  line. 

Another  piece  on  which  the  production  was  increased  con- 
siderably is  shown  at  E  in  Fig.  2.  This  is  a  thumb-screw  made 
from  i -inch  machine  steel  on  a  f-inch  Cleveland  automatic 
screw  machine,  which  had  been  changed  to  take  i-inch  stock. 
This  piece  was  first  made  on  a  Cleveland  automatic  having  a 
single-acting  cross-slide,  that  is,  the  front  and  back  tools  were 
mounted  on  the  same  slide  and  could  not  be  operated  inde- 
pendently. The  order  of  operations  for  making  this  screw  by 
this  method  is  as  follows : 


Order  of  Operations 

Feed  stock  to  stop 

Form 

Knurl  from  turret 

Thread  on  and  off 

Cut-off 

Total  number  of  revolutions  to  make  one  piece . 


Revo- 
lutions 
30 
275 

IOO 

40 
300 

745 


Sec- 
onds 
6 

55 

20 

8 

60 
149 


RECESSING  265 

This  order  of  operations  gave  a  gross  product  of  240  pieces 
in  ten  hours.  To  increase  the  production  of  this  piece,  it  was 
transferred  to  a  Cleveland  machine  which  had  a  double  inde- 
pendent cross-slide,  thus  enabling  the  cut-off  and  form  tool 
to  be  operated  at  the  same  time.  A  cross-slide  knurling  tool 
was  also  used  on  the  cross-slide,  obviating  the  necessity  of 
putting  it  in  the  turret.  The  order  of  operations  for  this  piece 
is  as  follows,  and  it  can  be  seen  that  a  considerable  increase 
was  the  result  of  this  change. 

Revo-  Sec- 
Order  of  Operations                                                       lutions  onds 

Feed  stock  to  stop 30  6 

Cut-off 300  60 

Knurl,  attached  to  cut-off  tool 

Form,  while  cutting  off (275)  (55) 

Thread  on  and  off    40  8_ 

Total  number  of  revolutions  to  make  one  piece 370  74 

The  gross  product  by  this  method  was  486  pieces  in  ten 
hours,  or  over  twice  that  of  the  previous  method. 

A  Recessing  Operation.  —  The  piece  shown  in  Fig.  5  gave 
considerable  trouble  before  it  was  made  successfully  on  the 
automatic  screw  machine.  This  piece  was  made  from  machine 
steel  |  inch  in  diameter,  in  a  No.  o  Brown  &  Sharpe  automatic 
screw  machine.  In  considering  the  speed,  it  was  found  that 
for  forming  the  stock  could  run  at  about  80  feet  per  minute, 
and  at  30  feet  per  minute  for  thread  cutting.  Therefore,  the 
spindle  speeds  required  are  611  and  603  revolutions  per  minute, 
respectively,  but,  by  referring  to  the  table,  it  will  be  found 
that  the  nearest  spindle  speed  is  663  revolutions  per  minute. 

The  recessing  is  performed  with  a  Brown  &  Sharpe  standard 
swing  tool,  which  is  the  tool  usually  selected  for  this  class  of 
work.  The  recessing  cutter  is  first  fed  at  right  angles  to  the 
spindle  by  the  cross-slide,  after  which  it  is  fed  forward  by  the 
turret.  The  feeds  given  in  the  following  were  found  to  be 
sufficiently  light,  and  the  tools  stood  up  well  without  continual 
sharpening. 

The  method  of  setting  the  circular  tools  on  the  machine  is 
shown  to  the  right  in  Fig.  5.  The  circular  form  tool  A  is  lo- 
cated on  the  back-slide,  and  the  cut-off  tool  B,  on  the  front- 


266  SCREW  MACHINE  PRACTICE 

slide.  The  form  tool  operates  while  the  hole  is  being  drilled; 
this  is  practicable,  because  the  smallest  diameter  to  be  formed 
is  0.245  inch,  while  the  diameter  of  the  drilled  hole  is  0.161 
inch.  The  surface  speed  of  the  drill  is  only  28  feet  per  minute, 
as  the  machine  spindle  cannot  be  run  faster  on  account  of 
threading.  Some  operators  prefer  a  high-speed  drilling  attach- 
ment for  this  kind  of  work.  The  order  of  operations  for  making 
this  piece  is  as  follows : 

Revo-  Hun- 
Order  of  Operations  lutions  dredths 

Feed  stock  to  stop 13  3 

Form  —  o.i  28-inch  rise  at  o.ooi-inch  feed (128)  (29) 

Revolve  turret 13  3 

Center —  o.ogo-inch  rise  at  o.oo5-inch  feed 18  4 

Revolve  the  turret 13  3 

Drill  —  o.5i2-inch  rise  at  o.oo4-inch  feed 128  '29 

Revolve  the  turret 13  *  3 

Recess  —  o.o5o-inch  rise  at  o.oo28-inch  with  rear  cross-slide .  .  18  4 

Recess  from  turret  —  o.25o-inch  rise  at  o.oo5i-inch  feed.  ...  49  n 

Drop  back  rear  cross-slide 9  2 

Revolve  turret 13  3 

Thread  in 9  2 

Thread  out 9  2 

Cut-off  —  o.274-inch  rise  at  o.oo2-inch  feed 137  31 

Revolve  turret  twice (26)  (6) 

Total  number  of  revolutions  to  make  one  piece 442  100 

With  this  lay-out,  a  piece  is  made  every  40  seconds,  which 
means  a  gross  production  of  900  pieces  in  ten  hours.  The 
cams  for  this  piece  are  shown  in  Fig.  6  and  consist  as  usual 
of  the  lead,  front-slide,  and  back-slide  cams.  It  will  be  noticed 
that  the  rear-slide  cam  has  a  lobe  of  from  45  to  60  on  the  cam 
circle.  The  use  of  this  portion  is  as  follows :  At  45  the  recess- 
ing tool  is  brought  into  place  by  the  lead  cam,  the  rear-slide 
cam  moves  forward  0.050  inch,  feeding  the  recessing  tool  in 
to  take  the  depth  of  chip  required.  Then  at  from  49  to  60 
the  form  cam  has  a  dwell  while  the  recessing  tool  moves  for- 
ward; the  allowance  from  60  to  62  is  made  to  withdraw  the 
back  slide  before  withdrawing  the  swing  tool. 

Drilling  and  Counterboring  from  Cross-slide.  —  Hand  screw 
machine  operations  are  frequently  performed  on  work  partly 
made  in  the  automatic  machines,  because  in  order  to  complete 
the  work  in  the  automatic  machine  it  would  require  seven 
tools,  which  exceeds  the  number  of  holes  in  the  turret  of  a 


DRILLING  AND  COUNTERBORING 


267 


Brown  &  Sharpe  automatic  screw  machine.  At  A,  in  Fig.  7, 
is  shown  a  piece  of  work  knurled  on  one  end,  which  was  made 
in  a  No.  2  Brown  &  Sharpe  automatic  screw  machine.  Unless 
a  combination  counterbore  is  used,  the  list  of  turret  tools 
required  will  be  a  stop,  center,  drill,  reamer,  two  counterbores, 
and  a  knurl. 

The  method  used  in  holding  the  extra  counterbore  is  shown 


CUT  OFF 
0.274 


FRONT. 
REAR 


Machinery 


Fig.  6.   Cams  used  in  Making  the  Piece  shown  in  Fig.  5 

at  A  in  Fig.  8.  The  counterbore  is  held  in  a  holder  placed 
on  the  cross-slide,  and  when  the  counterbore  is  in  line  with 
the  hole  in  the  work  it  is  fed  forward  by  means  of  the  stop 
in  the  turret  coming  against  the  rear  end  a  of  the  counterbore. 
The  counterbore  is  made  a  good  sliding  fit  in  the  hole  in  the 
boss,  and  is  prevented  from  turning  by  the  headless  screw  b. 
A  pin  driven  into  the  shank  of  the  counterbore  and  a  helical 
spring  assist  in  keeping  the  counterbore  in  the  "back"  position. 


268  SCREW  MACHINE  PRACTICE 

The  order  of  operations  for  producing  the  piece  shown  at  A 
in  Fig.  7  is  as  follows : 

Revo-  Hun- 
Order  of  Operations  lutions  dredths 

Clearance 19.6  2 

Feed  stock  to  stop 19.6  2 

Revolve  turret 19.6  2 

Center  —  o.i  25-inch  rise  at  o.oo63-inch  feed 19.6  2 

Revolve  turret 29.4  3 

Drill  —  o.5oo-inch  rise  at  o.oo56-inch  feed 88.2  9 

Revolve  turret 29.4  3 

Ream  —  o.5oo-inch  rise  at  o.oo72-inch  feed 137.2  14 

Revolve  turret 29.4  3 

Counterbore  —  o.iso-inch  rise  at  o.ooi4-inch  feed 107.8  n 

Revolve  turret 29.4  3 

Knurl  on  —  o.3oo-inch  rise  at  o.oio2-inch  feed 29.4  3 

Knurl  off  —  o.3OO-inch  rise  at  o.oi  53-inch  feed 19.6  2 

Revolve  turret 29.4  3 

Advance  front  slide  and  dwell 88.2  9 

Counterbore  from  cross-slide  —  o.i  25-inch  rise  at  0.002 i-inch 

feed (58.8)  (6) 

Clearance (19.6)  (2) 

Cut-off  —  o.477-inch  rise  at  o.ooi67-inch  feed 284.2  ^9 

Total 980.0  100 

The  cams  for  producing  the  piece  shown  at  A  in  Fig.  7  are 
shown  in  Fig.  9,  where  the  various  functions  of  the  lobes 
are  clearly  indicated.  The  most  interesting  lobe  on  this  set 
of  cams  is  the  lobe  on  the  cross-slide  cam  from  63  to  71,  which 
brings  the  special  Counterbore  shown  at  A  in  Fig.  8  in  line 
with  the  hole  in  the  work.  The  stop  in  the  turret  used  for 
feeding  in  this  counterbore,  and  which  is  also  used  for  gaging 
the  stock  to  length,  is  operated  by  the  lobe  from  63  to  69  on 
the  lead  cam.  It  will  be  noticed  that  this  lobe  is  much  lower 
than  the  lobe  from  2  to  4  gaging  the  stock  to  length,  the  reason 
being  that  the  counterbore  projects  much  further  from  the 
chuck  than  does  the  stock  when  fed  out. 

Another  simple  method  of  holding  an  extra  tool  on  the  cross- 
slide  is  illustrated  at  B  in  Fig.  8.  Here  the  holder  is  made 
so  that  it  will  take  either  a  drill  or  a  counterbore,  which  is  held 
in  it  by  means  of  a  headless  screw.  The  tool  is  rotated  by 
means  of  the  grooved  pulley  c,  which  is  fastened  to  the  spindle 
d  as  shown.  This  pulley  is  driven  from  the  overhead  works 
by  a  round  belt,  which  is  left  sufficiently  slack  to  allow  the 
front  cross-slide  to  advance  to  a  position  in  line  with  the  work. 


DRILLING  AND   COUNTERBORING 


269 


The  drill  is  fed  forward  by  a  stop  held  in  the  turret,  and  is 
withdrawn  by  the  coil  spring  e. 

Other   operations  performed   with   drills  and   counterbores 
held  on  the  cross-slide  are  shown  in  Fig.  7  at  Bj  C,  D,  and  E, 


0.30  u_ 


Machinery 


Fig.  7.  Samples  of  Work  operated  on  by  Counterbores  and  Drills  held  on 
the  Cross-slide 

respectively.  At  C  is  shown  a  piece  made  with  an  eccentric 
hole.  This  is  easily  produced  by  means  of  a  drill  held  in  a 
holder  fastened  to  the  cross-slide.  It  is  necessary  to  lock  the 
spindle  when  the  hole  is  being  drilled.  A  drill-holder  similar 


WASHER    „ 


\ 





1? 

p 

_0 

- 

7~~~ 



e 

<fT 

) 

> 



^ 

-J 

Machinery 


Fig.  8.   Holders  for  Carrying  Drills  and  Counterbores  on  the  Cross-slide 

in  construction  to  that  shown  at  B  in  Fig.  8  is  used.  The 
piece  shown  at  C  is  made  with  holes  having  different  degrees 
of  eccentricity;  otherwise  the  pieces  made  with  an  eccentric 
hole  are  of  the  same  size  and  shape.  It  is  interesting  to  com- 
pare this  method  of  drilling  with  the  old  method,  which  con- 


270 


SCREW   MACHINE   PRACTICE 


sisted  in  holding  the  stock  in  an  eccentric  chuck  or  in  drilling 
each  piece  in  a  drill  jig.  The  method  last  mentioned  is  ex- 
pensive, and  the  eccentric  chuck  method  is  very  destructive 
to  the  cut-off  tools,  owing  to  the  pounding  of  the  stock  against 
the  cutting  edge. 

At  B  is  shown  how  wrench  slots  were  produced  in  a  special 
nut.     The  holes  were  first  drilled,  after  which  the  shank  was 


11 


CAM  OUTLINES      59 

LEAD 
FRON 
REAR 


Machinery 


Fig.  9.   Cams  used  in  Producing  the  Piece  shown  at  A  in  Fig.  7 

turned  down  by  means  of  a  box-tool,  leaving  only  one-half 
of  the  drilled  holes  in  each  side.  To  produce  this  piece,  the 
cross-slide  cam  moves  the  drill  and  holder  forward  part  way, 
then  dwells  while  the  first  hole  is  being  drilled,  by  means  of 
a  stop  in  the  turret  forcing  the  drill  into  the  work.  After  the 
first  hole  is  drilled,  the  cam  advances  into  position  for  the 
second  hole,  when  the  same  operation  is  repeated.  At  D  is 
shown  a  washer  provided  with  two  holes  which  were  also  drilled 


MAKING  WATCH  PARTS 


271 


in  this  manner.  At  E  is  shown  a  piece  which  requires  a  differ- 
ent movement.  The  lead  cam  is  not  used  at  all,  and  the  groove 
a  is  cut  by  a  special  tool  held  on  the  cross-slide.  After  the 
machine  spindle  is  locked  in  position  by  means  of  the  brake, 
this  tool  starts  at  one  side  and  is  fed  across  by  the  cross-slide 
cam.  These  special  operations  give  little  trouble,  especially 
on  brass  work,  the  material  from  which  the  parts  described 
were  made. 

Making  Watch  Parts  in  the  Screw  Machine.  —  Watch- 
making by  automatic  machinery  is  essentially  an  American 
development.  Previous  to  the  inauguration  of  the  industry 


Machinery 


Fig.  10.  Blank  for  Watch  Pinion 
made  by  Forming  from  Tool- 
steel  Stock 


Fig.  11.  Blank  for  Watch  Wheel 
Staff  made  by  Turning  from 
Tool-steel  Stock 


in  Waltham,  Mass.,  Switzerland  held  the  lead  in  the  manufac- 
ture of  watches  on  a  large  scale.  The  hand  processes  there 
followed  are  the  result  of  long  experience  and  careful  study, 
and  the  work  is  highly  organized  so  far  as  the  division  of  labor 
is  concerned,  separate  workmen  specializing  on  single  opera- 
tions, which  they  repeat  day  after  day.  Swiss  watches  are 
not  handmade  in  the  sense  in  which  we  apply  that  term  to 
custom-made  footwear,  for  instance.  Lathes,  presses,  gear- 
and  pinion-cutters,  and  other  power-operated  machines  are 
used  in  the  various  operations  required.  These  tools  have, 
however,  been  largely  operated  by  hand  in  the  same  way  that 
ordinary  engine  lathes  are  operated,  as  distinguished  from  the 
mechanically-controlled  movements  of  the  automatic  gear- 
cutter  or  screw  machine. 

In  American  watchmaking  practice  the  automatic  principle 
has  been  developed  to  an  extent  that  is  little  short  of  mar- 


272 


SCREW  MACHINE  PRACTICE 


velous,  the  parts  not  only  having  complicated  operations 
performed  on  them  in  single  machines,  but  even  being  trans- 
ferred from  one  machine  to  another  automatically,  through  a 
long  series  of  operations.  The  various  manufacturers  of  watches 


FEED  STOCK 


OF  TURRET  IN 
BACKWARD  POSITION 


1ST  OPERATION 
POINT  WITH  POINTING  TOOL- 
IK  FLOATING  HOLDER 


2ND  OPERATION 
FORM  WITH  FRONT  AND 
BACK  SLIDE  TOOLS  — 
SUPPORT  WHILE  FORMING    ' 
WITH  TELESCOPIC  SUPPORT 
'IN  TURRET 


3RD  OPERATION 
CUT  OFF  WITH  ANGULAR  — 
CUTTING-OFF  TOOL 


Machinery 


Fig.  12.   Tools  used  and  Order  of  Operations  followed  in  Making  the  Pinion 
Blank  shown  in  Fig.  10 

in  this  country  have,  as  a  rule,  each  developed  their  own 
machinery,  although  the  automatic  screw  machines  made  by 
the  Brown  &  Sharpe  Mfg.  Co.  have  been  invading  this  highly 
specialized  field  of  watchmaking.  These  machines  have  also 
met  with  considerable  favor  in  the  Swiss  watchmaking  field, 
committed  though  it  is  by  years  of  precedent  to  the  use  of 


MAKING  WATCH  PARTS  273 

the  hand-operated  machine.  The  particular  work  for  which 
this  tool  has  been  applied  is  in  the  turning  of  the  larger  pinion 
blanks  and  staffs  (the  slender  shafts  or  spindles  on  which 
gears  and  pinions  are  mounted).  These  parts  have  to  be  made 
with  a  high  degree  of  accuracy,  both  as  to  their  dimensions 
and  as  to  their  concentricity,  or  the  trueness  with  which  they 
run  on  centers. 

Tools  and  Operations  for  Making  a  Pinion  Blank.  —  The 
part  shown  in  Fig.  10  is  one  of  the  larger  pinion  blanks  used 
in  a  Swiss  watch.  In  making  it  by  the  old-fashioned  methods, 
a  blank  is  cut  off  and  formed  at  each  end  with  the  cone  points 
shown,  which  are  supported  in  female  centers  in  the  lathe, 
where  successive  cuts  are  taken  to  bring  it  to  the  required 
dimensions,  the  same  as  would  be  done  for  much  larger  work 
in  the  engine  lathe.  This  operation  is  practically  duplicated 
in  the  automatic  screw  machine,  so  far  as  turning  on  centers 
is  concerned. 

The  order  of  operations  and  the  tools  used  for  each  of  them 
may  be  followed  from  Fig.  12.  The  first  operation  is  the  feed- 
ing of  the  stock.  No  stop  is  used  for  the  stock  to  feed  against, 
the  feeding  mechanism  being  accurate  enough  to  always  leave 
a  few  thousandths  of  stock  for  the  first  operation,  which  is 
that  of  pointing  the  end  of  the  bar  to  form  the  outer  cone- 
shaped  pivot  point  of  the  work.  This  is  done  by  a  tool  mounted 
in  a  "floating"  holder,  which  may  be  firmly  clamped  in  the 
proper  position  for  forming  an  accurately  pointed  pivot  each 
time  the  machine  is  set  up.  With  this  tool,  the  accurate  align- 
ment of  the  turret  with  the  axis  of  the  spindle  is  not  abso- 
lutely necessary;  in  fact,  no  alignment  accurate  enough  for 
this  purpose  could  be  permanently  maintained.  This  piece 
of  work  is  short  and  stiff  enough  so  that  it  can  be  turned  en- 
tirely by  circular  forming  tools  mounted  in  the  cross-slide. 
These  forming  tools  are  shown  at  work  in  the  second  operation 
in  Fig.  12.  The  one  in  the  front  cross-slide  turns  the  two 
diameters  forward  of  the  largest  diameter  on  the  work,  while 
the  rear  cross-slide  turns  the  two  diameters  on  the  other  side 
of  the  collar,  and  rough-turns  the  protecting  end  of  the  stock 


274 


SCREW  MACHINE  PRACTICE 


WORK 


for  the  cone  point  of  the  next  part  to  be  made.  While  these 
operations  are  in  progress,  the  outer  end  of  the  work  is  sup- 
ported in  a  delicate  female  center,  in  a  spring  plunger  held  in 
the  turret.  It  was  stated  that  this  part  is  practically  turned 
on  centers.  The  significance  of  this  statement  will  be  under- 
stood by  studying  the  second  operation,  and  the  succeeding 
or  third  operation.  Since  the  outer  end  of  the  work  is  sup- 
ported by  the  center  while  the  forming  is  in  progress,  the  di- 
ameters thus  turned  must  be  true  with  that  center.  In  the 

third  operation,  the  center 
at  the  other  end  of  the  work 
is  formed.  The  forming  of 
this  center  is  shown  in  Fig. 
13.  The  blade  follows  a 
diagonal  line  of  travel,  so 
that  the  center  is  turned  to 
the  right  angle.  Face  a  is 
beveled  so  that  it  clears  the 
work  entirely,  and  the  point 
is  quite  sharp.  The  cutting 
action  is  thus  entirely  on  the 
face  of  the  stock,  and  the 
work  is  not  subject  to  any  pressure  whatsoever,  but  remains 
attached  to  the  stock  until  the  tool  has  progressed  so  far  that 
it  separates  and  falls  off  by  its  own  weight,  leaving  the  point  so 
sharp  as  to  be  for  all  practical  purposes  a  perfect  one.  The 
outside  diameter  of  the  piece  is  left  stock  size.  This  large 
diameter  has  the  pinion  teeth  cut  in  it  and  runs  true  enough 
for  all  practical  purposes. 

Cone-point  Turning  and  Cutting-off  Tool.  —  The  construc- 
tion of  the  point  turning  tool  is  shown  in  Fig.  14.  The  cutting- 
off  blade  B  is  held  in  a  slot  in  tool-slide  C  and  rests  on  adjust- 
ing screw  D  and  pin  E.  It  is  clamped  in  position  by  screw 
F.  By  adjusting  screw  D,  the  blade  is  rocked  about  pivot  E 
to  bring  the  point  higher  or  lower  as  may  be  required  to  accu- 
rately center  it  with  the  axis  of  the  work.  Slide  C  is  gibbed 
to  a  dovetail  guide  on  slide  carrier  G.  This  member  is  pivoted 


LINE  OF  TRAVEL 
OF  THE  TOOL 


Machinery 


Fig.  13.  The  Cone  Point  Turning  and 
Cutting-off  Operation 


MAKING  WATCH  PARTS 


275 


to  the  body  of  the  tool  H  about  the  axis  of  bolt  /,  and  is  clamped 
by  screw  K  in  the  proper  location  to  guide  the  slide  C  in  form- 
ing the  desired  angle  for  the  pivot  of  the  work. 

Tool-slide  C  has  attached  to  it  a  rack  which  meshes  with 
the  32-pitch  pinion  L,  pivoted  to  the  under  side  of  G.  Pinion 
L  meshes  with  a  similar  pinion  M ,  pivoted  in  a  hole  in  the  body 


SECTION  ON  LINE  X-X 


ADJUSTMENT  OF  BLADE 
IN  TOOL-HOLDER 


TOP  VIEW 
WITH  TOOL-HOLDER  REMOVED 


FRONT  VIEW 
WITH  TOOL-HOLDER  REMOVED 


SIDE  ELEVATION 

WITH  TOOL-HOLDER  REMOVED     Machinery 


Fig.  14.   Construction  of  Cone  Point  Turning  and  Cutting-off  Tool 

of  the  tool  about  the  center  of  bolt  /,  so  that  the  correct  rela- 
tions between  them  are  preserved  whatever  the  angular  ad- 
justment of  G  on  H.  Pinion  M  is  lengthened  and  at  its  lower 
extremity  meshes  with  rack  teeth  cut  in  the  side  of  plunger  N. 
This  is  best  seen  in  the  section  on  line  xx.  This  plunger,  as  may 
be  seen  in  the  side  elevation,  has  at  its  front  end  a  projection 
extending  upward  bearing  against  a  plunger  0  in  a  hole  above 
it,  which  is  pressed  outward  by  a  spring.  By  this  means,  N 
is  normally  kept  at  the  outer  end  of  its  movement,  being 
limited  in  this  direction  by  the  seating  of  screw  P  in  the  recess 


276 


SCREW   MACHINE   PRACTICE 


I       FACE  OF  TURRET  IN 
BACKWARD  POSITION 


1ST  OPERATION 

POINT  WfTH  BOX  POINTING 

TOOL 


2ND  OPERATION 

TURN  LARGE  SHOULDER  A 

USING  SWING  TOOL    — 

WITH  TELESCOPIC 

SUPPORT 


3RD  OPERATION 
TURN  INTERMEDIATE 

SHOULDER  B 

TOOL  USED  IS  A  DUPLICATE 

OF  TOOL  USED  FOR 

2ND  OPERATION 


4TH  OPERATION 

TURN  SMALL  DIAMETER  C 

TOOL  USED  IS  A  DUPLICATE 

OF  TOOL  USED  FOR 

2ND  OPERATION 


6TH  OPERATION 
FORM  WITH  BACK  SLIDE  TOOL 
FORM  WITH  FRONT  SLIDE  TOOL 

SUPPORT  WHILE  FORMING 

WITH  TELESCOPIC  SUPPORT 

IN  TURRET 


6TH  OPERATION 

CUT  OFF  WITH  ANGULAR 

CUTTING  OFF  TOOL 


Machinery 


MAKING  WATCH  PARTS  277 

provided  for  it  in  the  body  H  of  the  tool.  In  this  position,  the 
tool-slide  is  withdrawn  so  that  the  blade  clears  the  work. 

The  front  end  of  N  is  provided  with  knurled  screw  Q  and 
lock-nut  R.  These  are  so  located  as  to  be  in  line  with  a  pusher 
or  raising  plate  attached  to  the  front  cross-slide  of  the  machine, 
when  the  turret  has  brought  the  tool  to  the  proper  position 
for  cutting  off.  The  cutting  off  is  effected  by  the  movement 
of  the  cross-slide.  The  pusher  bears  on  screw  Q,  presses  plunger 
N  inward,  revolving  pinions  M  arid  L,  which,  in  turn,  acting 
on  the  rack  attached  to  the  tool-slide,  move  cutter  B  inward, 
severing  the  work  from  the  bar  and  forming  the  pivot  point, 
as  shown  in  Fig.  13.  The  length  of  the  inward  travel  of  the 
tool  is  adjusted  by  screw  Q  and  lock-nut  R.  The  swiveling 
adjustment  of  the  pusher  plate  is  not  needed  for  this  job. 

Cams  for  Making  Pinion  Blank.  —  At  A,  B,  and  C  in  Fig. 
1 6  are  shown  the  cams  by  which  the  feeding  movements  of 
the  machine  are  effected  for  performing  the  operations  shown 
in  Fig.  12.  As  is  well  known,  the  Brown  &  Sharpe  automatic 
screw  machine  has  a  front  and  a  back  cross-slide  and  a  turret- 
slide,  each  controlled  by  its  own  separate  plate  cam.  In  Fig. 
1 6  the  various  radial  lines  are  figured  to  show  their  distance 
from  the  starting  point  o,  in  hundred ths  of  a  circle.  The 
various  acting  surfaces  of  the  cams  are  marked  to  indicate 
the  operations  performed  by  them.  The  material  used  for 
this  pinion  blank  is  tool  steel.  The  spindle  revolves  1320 
revolutions  per  minute,  giving  a  surface  speed  to  the  work 
of  about  58  feet  per  minute,  which  is  suitable  for  the  material 
used  with  the  heavy  flow  of  oil  directed  on  the  cutting  edges 
of  the  tools.  It  takes  770  revolutions  to  make  a  piece,  so  that 
each  hundredth  of  a  revolution  of  the  cam  represents  7.7 
revolutions  of  the  spindle.  Knowing  this,  the  various  feeds 
can  be  readily  figured  out.  On  the  back-slide  cam,  which  takes 
the  wider  of  the  two  forming  cuts,  a  finer  finishing  feed  is  used 
between  positions  60  and  72^  than  for  the  first  portion  of  the 
forming  between  20  and  60.  This  is  done  to  produce  the 
finer  finish  which  the  finer  feed  gives.  It  will  also  be  noticed 
that  in  all  forming  operations,  such  as  those  performed  by  the 


278 


SCREW   MACHINE   PRACTICE 


MAKING  WATCH  PARTS  279 

two  cross-slides,  and  by  the  turret-slide  in  pointing  the  work 
in  the  first  operation,  the  cams  are  provided  with  " dwells," 
or  resting  places  where  the  periphery  of  the  cam  is,  for  a  short 
space,  a  portion  of  the  circumference  of  a  circle,  so  that  the 
slide  is  allowed  to  rest  at  this  point  while  the  chip  runs  out. 
This  produces  a  smooth  final  finish.  The  net  production  is 
900  per  day,  allowing  time  for  sharpening  tools,  etc. 

Tools  and  Operations  for  Making  a  Watch  Staff. —  The 
part  shown  in  Fig.  n  has  to  be  handled  somewhat  differently 
from  the  one  just  considered.  It  is  much  longer  and  more 
slender,  and  cannot  be  formed  by  cross-slide  tools.  The  order 
of  operations  is  indicated  in  Fig.  15.  The  stock,  having  been 
fed  to  length,  is  pointed  by  the  turret  tool  shown  in  the  first 
operation.  In  this  tool  the  stock  is  supported  by  a  bushing 
while  the  end  is  being  pointed,  the  work  being  too  slender  to 
support  itself,  as  in  Fig.  12.  In  the  second  operation,  shoulder 
A  is  turned.  This  is  done  by  a  swing  tool.  The  pointed  end 
is  supported  in  a  female  center,  a  turning  cut  is  taken  over  the 
shoulder  of  the  finished  diameter  required,  the  cutting  blade 
is  released  so  that  it  is  not  dragged  over  the  work  on  the 
return,  and  then  the  turret  is  revolved  for  the  next  opera- 
tion. Operations  3  and  4  are  also  performed  by  the  same 
kind  of  a  tool  and  in  the  same  way,  shoulders  B  and  C  being 
each  finished  in  turn.  It  will  be  noticed  that  the  smallest 
diameter  is  finished  last.  If  shoulder  C  were  turned  first  to 
its  finished  size,  it  would  not  be  stiff  enough  to  support  the 
succeeding  cuts  A  and  B,  with  assurance  that  they  would  be 
true  with  the  cone-pointed  end. 

In  the  fifth  operation,  the  work  is  supported  in  a  female 
center  while  formed  tools  in  the  front  and  rear  cross-slides 
square  up  the  shoulders  already  turned,  and  remove  the  burrs 
caused  by  the  turning  tools.  The  front  cross-slide  tool  forms 
the  small  diameter  to  the  left  of  the  collar  and  squares  up  the 
sides  of  the  collar  itself.  As  will  be  seen  from  a  study  of  the 
cams  D,  E,  and  F,  Fig.  16,  the  front  cross-slide  tool  does  not 
begin  to  cut  until  the  one  in  the  rear  has  completed  its  work. 
The  stock  is  too  slender  to  permit  of  too  much  work  being  done 


280 


SCREW   MACHINE   PRACTICE 


on  it  at  once.  In  the  sixth  operation,  the  same  angular  cutting- 
off  tool  as  shown  in  Fig.  14  is  used  for  severing  the  work  from 
the  bar  and  forming  the  cone  point  at  the  same  time.  It  will 
be  seen  that  in  the  operations  just  described,  as  in  the  previous 
case,  the  various  diameters  will  be  as  concentric  with  the  pointed 
centers  of  the  work  as  if  they  had  been  turned  on  them. 


Machinery 


Fig.  17.    Swing  Tool  used  for  Operations  on  Part  Shown  in  Fig.  15 

Operation  of  the  Swing  Tool.  —  The  swing  tool  used  in 
Operations  3,  4,  and  5  in  Fig.  15  is  shown  in  Fig.  17.  To  the 
body  T  of  the  device  is  pivoted  (about  stud  U)  the  tool-holder 
V,  carrying  blade  W,  which  is  adjusted  vertically  and  clamped 
by  the  square-headed  screws  shown.  In  a  hole  drilled  into 
the  body  of  the  tool  is  contained  a  plunger  Z  pressed  outward 
by  a  spring.  The  opening  of  this  hole  is  closed  by  a  screw, 
as  shown.  A  pin  X  driven  into  the  side  of  tool-holder  V  pro- 
jects through  a  side  hole  into  T,  and  bears  on  the  face  of 
plunger  Z.  By  this  means,  the  spring  keeps  V  swung  outward, 
the  movement  being  limited  by  the  bearing  of  Z  on  the  head- 
less set-screw.  Abutment  screw  F,  in  part  V,  is  in  position  to 
bear  against  the  pusher  or  raising  plate  carried  by  the  cross- 
slide. 

In  turning  shoulders  A,  B,  and  C  (Fig.  15),  the  movements 


MISCELLANEOUS   EXAMPLES  281 

of  the  front  cross-slide  and  turret-slide  cams  are  so  arranged 
that  the  swing  tool  is  brought  up  to  the  work ;  the  cross-slide 
is  next  moved  in  to  set  the  tool  W  to  the  diameter  desired,  as 
determined  by  the  adjustment  of  screw  F;  then  the  swing 
tool  is  fed  forward  the  proper  distance  for  the  shoulder.  The 
front  cross-slide  is  next  withdrawn,  allowing  tool  W  to  swing 
outward  under  the  influence  of  the  spring  and  plunger  Z. 
The  turret-slide  then  retreats,  drawing  the  blade  out  of  the 
way  without  allowing  it  to  drag  on  the  work.  The  swivel 
adjustment  on  the  raising  plate  allows  either  straight  or  taper 
turning  to  be  done,  as  required. 

The  Cam  Equipment.  —  The  cams,  shown  at  D,  E,  and  F 
in  Fig.  1 6,  for  making  the  part  shown  in  Fig.  n  appear  to  be 
somewhat  complicated,  but  the  operations  may  be  easily 
followed.  The  various  lobes  of  the  three  cams  are  marked  for 
the  operations  for  which  they  are  intended.  The  abbrevia- 
tion "I.  T."  means  "index  turret,"  and  the  term  " dwell" 
indicates  a  concentric  portion  of  the  cam,  where  the  slides 
are  at  rest.  In  making  this  piece,  the  spindle  revolves  at 
2400  revolutions  per  minute.  The  stock  is  0.063  inch  in  di- 
ameter, which  gives  a  surface  speed  of  about  40  feet  per  min- 
ute. The  material  is  tool  steel.  The  net  production  for  these 
pieces  was  1500  per  day.  The  total  revolutions  to  make  one 
piece  is  840,  so  that  each  hundredth  on  the  periphery  of  the 
cams  represents  8.4  revolutions. 

Examples  of  Work  on  Cleveland  Automatic.  —  The  suc- 
cessive operations  for  produqing  the  parts  shown  in  Fig.  18, 
on  the  Cleveland  automatic,  will  be  described.  The  special 
chrome-nickel  steel  sleeve  shown  at  A  requires  drilling,  form- 
ing, recessing,  and  tapping.  A  3^-inch  model  A  machine 
with  a  No.  4  spindle  drive  is  used.  As  shown  in  Fig.  19,  the 
operations  are  in  the  following  order : 

1.  Gage  the  stock  to  length  by  a  gage  stop  A  in  the  first 
hole  in  the  turret. 

2.  Index    the    turret    and    rough-turn    the    large    diameter 
with  cutter  a,  using  an  overhanging  turning  attachment  B, 
and  at  the  same  time  drill  a  large  hole  full  depth,  using  a  drill 


282 


SCREW  MACHINE  PRACTICE 


and  split  holder  C  in  the  second  hole  in  the  turret;    time  of 
operations,  3  minutes  35  seconds. 

3.  Index  the  turret  and  finish- turn  the  large  diameter  with 
the  second  cutter  b  held  in  a  turning  attachment,  and  at  the 
same  time  counterbore  a  large  hole,  using  a  counterbore  and 
holder  D  held  in  the  third  hole  in  the  turret.  As  no  tools 
are  in  the  way  on  the  front  side,  forming  tools  E  and  F  can 
be  brought  into  operation  to  face  the  end  and  to  form  the  rear 


fftf— 
A  CHROME  NICKE'L  STEEL 


Machinery 


C.R.  STEEL 


Fig.  18.   Examples  of  Work  done  on  Cleveland  Automatic 

diameters,  using  flat  forming  tools  and  a  toolpost,  and  an 
open-side  toolpost  on  the  front  of  the  cross-slide.  The  time 
for  these  operations  is  4  minutes  30  seconds. 

4.  Index  the  turret  and  drill  a  small  hole,  using  a  drill  and 
splif  holder  G  in  the  fourth  hole  in  the  turret.    Time  of  opera- 
tion is  2  minutes  15  seconds. 

5.  Index  the  turret,  recess,  using  a  recessing  tool  and  holder 
H  in  the  fifth  hole  in  the  turret.     The  operating  cam  for 
effecting   a  movement  of   the  recessing  tool  is  held  on   the 
front  of  the  cross-slide.    Time  of  operation  is   i  minute  25 
seconds. 

6.  Index  the  turret  and  bring  the  tap-holder  I  and  tap  held 


MISCELLANEOUS   EXAMPLES 


3RD  FINISH  TURN,  COUNTERBORE, 


6TH  AND  7TH  TAP  AND  CUT-OFF 


Fig.  19.  Tool  Equipment  and  Operations  for  Making  a  Chrome-nickel  Steel  Sleeve 
on  a  "  Model  A"  Cleveland  Automatic 


284  SCREW  MACHINE  PRACTICE 

in  the  sixth  hole  into  operation.  The  time  for  threading  this 
piece  is  i  minute  45  seconds. 

7.  Cut  off,  using  the  cut-off  blade  /  held  in  a  universal 
cut-off  toolpost  on  the  rear  of  the  cross-slide.  Time  for  opera- 
tion is  i  minute  30  seconds. 

The  total  time  for  the  entire  operations  enumerated,  includ- 
ing the  idle  motions  of  the  machine,  is  15  minutes.  When  the 
tools  have  been  set  in  their  proper  relation  to  each  other,  and 
the  feed-regulating  cams  have  been  so  adjusted  as  to  give  the 
proper  feeds  for  the  various  tools,  the  position  of  the  various 
cams  is  noted  and  recorded  on  a  chart.  All  the  tools  used  are 
also  recorded  on  this  chart,  so  that  the  machine  can  easily 
and  quickly  be  equipped  and  adjusted  for  reproducing  this 
same  part,  if  necessary,  at  any  future  time. 

Another  comparatively  simple  piece  of  work  to  produce 
on  the  Cleveland  automatic  is  shown  at  B  in  Fig.  18.  The 
successive  operations  are  shown  in  Fig.  20,  the  machine  being 
a  3^-inch  Model  A,  using  the  No.  i  drive : 

1.  Feed  the  stock  to  stop  A,  which  is  held  in  the  first  hole 
in  the  turret. 

2.  Index  the  turret  and  drill  a  hole  full  depth,  using  a  drill- 
holder  B  in  the  second  hole  in  the  turret.    Time  for  operation, 
50  seconds. 

3.  Index  the  turret  and  finish- turn  the  outside  diameter 
with   an   overhanging   turning   attachment   D,    carrying   two 
cutting  tools  —  tool  a  for  roughing  and  tool  b  for  finish-turning. 
At  the  same  time,  counterbore  the  hole,  using  a  counterbore 
held  in  holder  E  in  the  third  hole  in  the  turret,  and  form  and 
face  with  tools  F  and  G  which  are  held  on  the  front  part  of 
the  cross-slide,  using  a  post  with  flat  cutters  and  spacing  blocks 
to  locate  them  the  correct  distance  apart.    Time  for  the  opera- 
tion, 3  minutes  55  seconds. 

4.  Index  the  turret  and  finish-turn  with  the  second  cutter 
b  in  an  overhanging  turning  attachment  D,  and  ream  the  hole, 
using  a  reamer  and  floating  holder   H  carried  in  the  fourth 
hole  in  the  turret.     The  time  for  these  two  operations  is  18 
seconds. 


MISCELLANEOUS   EXAMPLES 


1ST  GAGE  STOCK  TO   LENGTH 


2ND   DRILL  HOLE          B  V 


n_A 


3RD  FINISH  TURN,  COUNTERBORE   LARGE   HOLE, 
FORM  AND  FACE 


4TH  AND  STH  FINISH  TURN,  REAM  AND  CUT-OFF 


Machinery 


Fig.  20.  Tools  for  Making  a  Clutch  Case  on  a  "Model  A"  3^-inch 
Cleveland  Automatic 

5.  Index  the  turret  and  cut  off  with  a  universal  cut-off, 
tool  blade  /  and  post  held  on  the  rear  of  the  cross-slide.  Time, 
32  seconds. 

The  total  time,   including  the  idle  motions  for  chucking, 


286  SCREW  MACHINE  PRACTICE 

advancing,  and  withdrawing  the  turret  and  indexing,  is  5 
minutes  35  seconds.  The  arrangement  of  the  forming  and 
cutting-ofT  tools  is  shown  in  Fig.  23.  All  the  data  obtained 
from  the  setting-up  of  this  job  are  recorded  on  the  operation 
sheet,  as  well  as  any  particular  features  necessary  to  turn 
out  this  job  more  effectively.  All  the  tools  and  attachments 
are  noted  under  the  various  headings  on  the  sheet,  as  well 
as  the  size  of  the  pulleys,  number  of  pins  in  the  regulating  drum, 
and  other  points  regarding  the  proper  setting-up  of  the  machine. 
In  producing  the  twin  gear  blank  shown  at  C  in  Fig.  18, 
the  greatest  amount  of  work  is  done  from  the  cross-slide.  The 
drilling  depth  is  considerable,  so  that  the  best  way  to  lay  out 
this  job  would  be  to  use  two  drills,  one  going  in  part  way  and 
the  other  the  remainder  of  the  distance.  The  operations  on 
a  3|-inch  Model  A  machine  with  a  No.  i  drive  are  as  follows : 

1.  Gage  the  stock  to  length  by  a  stop  A   (Fig.  21)  held  in 
the  first  hole  in  the  turret. 

2.  Index  the  turret  and  turn  part  way  with  a  tool  a  in  an 
overhanging  turning  attachment  B  carrying  two  turning  tools, 
and  drill  part  way,  using  a  high-speed  drill  held  in  holder  C 
in  the  second  hole  in  the  turret.    Time  for  the  two  operations, 
40  seconds. 

3.  Index  the  turret  and  finish- turn,  using  the  second  cutter 
b  in  an  overhanging  turning  attachment  B,  and  drill  full  depth, 
using  a  high-speed  drill-holder  D  held  in  the  third  hole  in  the 
turret.    At  the  same  time,  advance  tools  E  and  F  held  on  the 
front  of  the  cross-slide  and  start  forming  the  rear  diameters. 
Also  take  a  cut  on  the  front  face,  using  tool  F  and  an  open-side 
toolpost  on  the  front  of  the  cross-slide.    Time  for  operations, 
i  minute  55  seconds. 

4.  Index  the  turret  and  ream  a  hole,  using  a  reamer  held 
in  a  high-speed  drill-holder  G  in  the  fourth  hole  in  the  turret. 
The  use  of  two  drills  on  a  hole  of  this  depth  avoids  the  necessity 
of  using  a  boring  tool,  and  the  reamer  in  this  case  can  be  held 
in  a  rigid  instead  of  a  floating  holder.    At  the  same  time  that 
the  hole  is  being  reamed,  three  cutting  blades  H,  held  on  the 
rear  of  the  cross-slide  and  separated  by  flat  spacing  blocks, 


MISCELLANEOUS  EXAMPLES 


287 


Fig.  21.    Successive  Operations  for  Producing  the  Twin  Gear  Blank 
Shown  at  C  in  Fig.  18 

are  brought  into  action.  The  grooving  blade  nearest  the  chuck 
is  made  considerably  wider  than  the  requirements  of  the  work 
demand,  and  is  used  for  roughing  the  front  end  of  the  next 
piece.  Time  for  operations,  3  minutes  40  seconds. 


288 


SCREW  MACHINE  PRACTICE 


2ND  TURN  SMALL  END-BOX-MILL 


Machinery 


Fig.  22.   Operations  for  Producing  the  Stanchion  Bolt  shown  at  D  in  Fig.  18 

5.  Index  the  turret,  and  counterbore  with  a  tool  held  in 
holder  I  in  the  fifth  hole  in  the  turret.     Time  for  operation, 
i  minute. 

6.  Cut   off   with   blade   /,    using   an    independent    cut-off 
attachment  shown  in  Fig.  24,  and  index  the  turret  twice.    Time 
for  operation,  35  seconds.    Total  time,  7  minutes  50  seconds. 

This  is  an  example  where  there  was  considerable  forming 
to  be  done  from  the  cross-slide,  which  could  not  be  handled 


MISCELLANEOUS   EXAMPLES  289 

efficiently  with  only  one  set  of  tools,  that  is,  using  only  one 
end  of  the  cross-slide  for  forming  tools;  consequently,  both 
ends  of  the  cross-slide,  as  shown  in  Fig.  24,  are  utilized  and 
the  work  is  then  cut  off  by  the  independent  cut-off  attachment 
shown.  For  the  operation  of  this  attachment  a  special  cam 
disk  A  is  held  on  the  rear  shaft  carrying  a  cam  B.  This  is 
adjustably  mounted  in  the  T-slot  groove  cut  in  the  side  of  the 
disk  and  can  be  set  in  any  desired  position.  This  cam  comes 
in  contact  with  a  roll  carried  in  the  rear  end  of  the  fulcrumed 
arm  of  the  attachment,  raising  it  up  and  consequently  depress- 
ing the  front  end  and  advancing  the  cutting-off  tool  toward 
the  center  of  the  work. 

The  stanchion  bolt  D,  Fig.  18,  brings  up  a  point  in  the 
operation  of  the  Cleveland  automatic  that  is  worthy  of  special 
attention;  that  is,  the  handling  of  long  forming  operations, 
especially  on  steel  parts.  This  can  be  done  much  more  effi- 
ciently by  means  of  a  long  flat  forming  tool  than  by  a  circular 
forming  tool.  There  are  two  reasons  for  this:  i.  The  flat 
forming  tool  gives  much  better  side  clearance  than  the  cir- 
cular tool.  2.  The  flat  forming  tool  can  be  held  much  more 
rigidly  and  heavier  cuts  can  be  taken  with  it.  It  is  also  much 
cheaper  to  make.  The  only  other  point  of  interest  about  this 
job  is  the  use  of  a  self-opening  die-holder.  The  use  of  this 
type  of  die  reduces  the  time  necessary  for  threading,  as  the  die 
does  not  need  to  be  backed  off,  but  is  opened  as  soon  as  the 
thread  is  completed,  and  the  turret  can  be  drawn  back  on  the 
fast  speed. 

Referring  to  Fig.  22,  it  will  be  seen  that  the  operations  are 
done  in  the  following  order,  a  2  f -inch  Model  A  machine 
equipped  with  a  No.  i  spindle  drive  being  used : 

1.  Gage  the  stock  to  length  with  a  gage  stop  A  held  in  the 
first  hole  in  the  turret. 

2.  Index  the  turret  and  turn  down  the  stem  with  a  box- tool 
B  held  in  the  second  hole  in  the  turret.    Time  for  this  operation, 
i  minute  30  seconds. 

3.  Index  the  turret  and  form  an  irregular  shape,  using  a 
flat  forming  tool  C  held  on  the  front  of  the  cross-slide ;  support 


2  go  SCREW  MACHINE  PRACTICE 

the  work  at  the  same  time  with  a  roller  steadyrest  D  held  in 
the  third  hole  in  the  turret,  and  engaging  the  stem  of  the 
work.  Time  for  this  operation  is  3  minutes  20  seconds. 

4.  Index  the  turret  and  thread,  using  a  self-opening  die- 
head  E  in  the  fifth  hole  in  the  turret.    Time  for  operation  is 
35  seconds. 

5.  Cut  off,  using  a  circular  cut-off  tool  F  held  on  the  rear 
of  the  cross-slide.     Time,  45  seconds. 

The  total  time,  including  all  the  idle  movements,  is  6  minutes 
15  seconds.  The  arrangement  of  the  tools  held  on  the  cross- 
slide  is  clearly  indicated  in  Fig.  25.  The  flat  forming  tool  C 
is  mounted  on  a  wedge  A  for  vertical  adjustment.  The  form- 
ing tool  is  held  down  by  the  cap-screws  and  the  wedge  is  ad- 
justed by  a  set-screw  D.  Another  set-screw  E  backs  up  the 
forming  tool,  supporting  it  much  more  rigidly.  The  cut-off 
tool  is  held  on  the  rear  forming  slide  and  is  turned  upside 
down  so  that  the  spindle  need  not  be  reversed,  the  cutting  off 
being  done  with  the  stock  running  in  the  forward  direction. 

Operations  on  Acme  Multiple-spindle  Machine.  —  The 
successive  order  of  the  operations  in  producing  a  long  set- 
screw  in  an  Acme  multiple-spindle  automatic  is  shown  in 
Fig.  26.  This  set-screw  is  made  from  a  square  wrought-iron 
bar.  The  threaded  portion  is  5!  inches  long,  the  length  over- 
all, 63;  |  inches.  The  longest  single  operation  consists  in  turning 
down  the  body  diameter  to  the  required  size.  The  spindle 
speed  at  which  to  rotate  the  work  should  first  be  determined. 
Taking  the  diameter  of  the  stock  across  the  flats  as  the  basis 
of  our  calculations,  and  deciding  on  a  surface  speed  of  100 
feet  per  minute,  it  will  be  found  that  the  desired  spindle  speed 
should  be  611  revolutions  per  minute.  The  nearest  available 
spindle  speed,  in  this  case,  is  635  revolutions  per  minute,  which 
gives  a  surface  speed  of  about  104  surface  feet  per  minute. 

The  next  step  is  to  determine  the  number  of  revolutions 
necessary  for  the  box-tool  to  travel  up  half  the  length  of  the 
screw  —  2 1  inches.  With  a  feed  of  0.0045  inch  per  revolu- 
tion of  the  work,  the  number  of  revolutions  required  to  make 
this  cut  is  about  640.  As  the  spindle  makes  635  revolutions 


USE   OF   MULTIPLE-SPINDLE   TYPE 


2QI 


Machinery 


Fig.  23.   Diagram  showing  Arrangement  of  Cross-slide  Tools  for  Forming 
and  Cutting  off  Piece  shown  at  B  in  Fig.  18 


Machinery 


Fig.  24.   Arrangement  of  Cross-slide  Tools  for  the  Forming  and  Cutting-off 
Operations  on  the  Part  shown  at  C  in  Fig.  18 


Machinery 


Fig.  25.   Arrangement  of  Cross-slide  Forming  and  Cutting-off  Tools  used 
in  Connection  with  Operations  shown  in  Fig.  22 


292  SCREW  MACHINE  PRACTICE 

per  minute,  the  time,  in  seconds,  to  turn  half  the  body  is 

60       640 

~  X  ~  ~  =  60.47  seconds.  Adding  to  this  the  time  for  the 
635  i 

idle  movements  of  the  machine  gives  60.47  +  2.4  =  62.87,  or, 
approximately,  63  seconds.  This  gives  a  product  of  57  pieces 
per  hour,  but,  upon  referring  to  the  table  of  change-gears, 
it  will  be  found  that  gears  to  give  this  product  are  not  ob- 
tainable. Therefore,  it  is  necessary  to  either  increase  the 
product  to  59  and  increase  the  feed  of  the  tools  accordingly, 
or  else  decrease  the  product  to  51  pieces  per  hour  with  a  cor- 
responding decrease  in  feed. 

The  tool  equipment  used  in  making  this  set-screw  is  illus- 
trated in  Fig.  27.  The  operations  start  in  the  first  position, 
where  the  first  box-tool  A  comes  into  position,  turns  up  half 
the  length  of  the  body  —  2|  inches  —  and  points  the  end  of 
the  screw.  At  the  same  time  that  the  box-tool  is  in  operation 
on  the  work,  the  form  tool  comes  in  from  the  side  and  turns 
down  the  neck  —  also  rough-forming  the  top  of  the  head.  As 
the  cylinder  is  indexed  into  the  second  position,  the  second 
box-tool  B  comes  into  operation  and  finish-turns  the  body. 
The  cylinder  is  again  indexed  to  the  third  position,  where  a  self- 
opening  die  C  cuts  the  thread.  After  threading,  the  cylinder 
is  again  indexed  and  the  piece  cut  off  with  a  straight-blade 
cut-off  tool  D.  These  various  operations  have  been  described 
separately,  but  in  actual  performance  all  tools  are  at  work  on 
different  bars  at  the  same  time. 

Making  Knurled  Thumb-nuts.  —  The  knurled  thumb-nut 
shown  at  A  in  Fig.  29  represents  an  example  in  which  the 
forming  is  the  longest  single  operation,  and  is  the  time  to  make 
one  piece.  This  knurled  nut  is  made  from  a  2 -inch  bar  of  round 
brass  rod  in  a  No.  56  Acme  multiple-spindle  automatic  screw 
machine.  The  first  step  in  determining  the  time  to  make  this 
piece  is  to  obtain  the  correct  speed  at  which  to  rotate  the  work. 
Rod  brass  can  be  worked  at  from  150  to  200  surface  feet  per 
minute,  and,  by  calculation,  it  will  be  found  that  a  spindle 
speed  of  290  revolutions  per  minute  will  give  150  feet  surface 
speed.  The  next  step  is  to  determine  the  proper  feed  at  which 


USE   OF   MULTIPLE-SPINDLE   TYPE 


293 


to  operate  the  form  tool.  Now  the  conditions  under  which 
this  thumb-nut  is  made  are  ideal,  as  far  as  a  heavy  feed  is  con- 
cerned, so  that  the  form  tool  can  easily  be  operated  at  0.005 
inch  per  revolution.  By  dividing  the  travel  of  the  form  tool 
or  0.635  inch  (allowing  o.oio  inch  to  approach  the  work) 


~~~L         FORM,  TURN  WITH  BOX-TOOL 

U"  .J  '"I.  ££?  HALF  WAY  AND  POINT 


FINISH  TURN  WITH  BOX-TOOL 


THREAD 


1ST  POSITION 


2ND  POSITION 


SRD  POSITION 


4TH  POSITION 


CUT-OFF 


Fig.  26.   Successive    Operations   for    Making   a   Long    Square-headed 
Set-screw 

by  0.005,  it  will  be  found  that  it  will  require  127  revolutions  of 
the  spindle  to  complete  the  forming  operation. 

As  this  is  a  case  where  the  longest  single  operation  is  per- 
formed from  the  form  tool-slide,  it  will  be  necessary  to  calcu- 
late the  time  required  in  seconds  to  complete  the  idle  move- 
ments of  the  machine.  This  is  found  to  be  4.6  seconds.  (For 
information  regarding  the  method  of  calculating  the  time  for 


294  SCREW  MACHINE  PRACTICE 

idle  movements,  see  Chapter  V.)  Then  the  time  in  seconds 
to  complete  the  forming  operation  equals  26.27  seconds.  Add- 
ing the  time  for  the  idle  movements  will  give  26.27  +  4.6  =  30.87 
seconds.  Assume  that  it  takes  30  seconds  to  make  one  piece ; 
then  the  rate  of  production  will  be  120  per  hour.  The  nearest 
production  to  this  for  which  change-gears  are  obtainable  is 
122  pieces;  and,  by  using  the  change-gears  to  obtain  this 
production,  the  feed  of  the  tools  is  increased  slightly,  which, 
in  this  case,  could  be  done  with  satisfactory  results. 

In  making  this  thumb-nut,  the  rough-forming  is  done  in 
the  first  position  and  the  hole  drilled  to  the  proper  depth 
with  drill  A  (see  Fig.  28).  In  the  second  position,  the  head  of 
the  nut  is  knurled  with  knurl  B,  and  the  hole  counterbored 
to  a  square  bottom,  both  operations  being  done  by  tools  held 
in  the  end- working  tool-slide.  The  hole  is  tapped  with  tap  C 
and  the  head  beveled  and  grooved  in  the  third  position, 
the  grooving  being  done  with  a  shaving  tool  D.  In  the  fourth 
position,  the  completed  nut  is  cut  off  from  the  bar  with  cut-off 
tool  E. 

Making  a  Part  Requiring  Cross-drilling.  —  The  brass  knob 
shown  at  B  in  Fig.  29  is  a  difficult  piece  on  which  to  determine 
the  longest  operation  at  a  glance.  It  is  evident,  however, 
that  the  drilling  of  the  large  hole  in  the  end  will  not  require 
much  time,  so  that  the  longest  operation  lies  between  the 
forming  and  cross-drilling  cuts.  The  depth  of  form  cut  is 
0.195  inch  and,  with  a  feed  of  0.002  inch  per  revolution,  it 
will  require  98  revolutions  of  the  spindle  to  complete  this 
operation. 

The  cross-drilling  attachment  is  held  on  the  cut-off  tool- 
slide,  as  shown  in  Fig.  30,  and  its  travel  is  governed  by  the 
feed  given  to  the  cut-off  tool.  As  the  cross-hole  is  deeper  than 
half  the  diameter  of  the  stock  to  be  severed  by  the  cut-off 
tool,  it  is  necessary  to  use  an  accelerating  cross-drilling  attach- 
ment. This  will  increase  the  rate  of  travel  of  the  attachment 
in  relation  to  the  cut-off  tool-slide  in  a  ratio  of  if  to  i.  The 
travel  of  the  cross-drill  is  equal  to  the  depth  of  the  hole  —  ^ 
inch  —  plus  the  length  of  point  on  the  drill  and  the  height  of 


Fig.  27.  Tool  Equipment  for  Producing  the  Set-screw  shown  in  Fig.  26  on  Acme 
Multiple-spindle  Automatic  Screw  Machine 


Fig.  28.  Tool  Equipment  for  Producing  a  Brass  Thumb-nut 


296  SCREW  MACHINE  PRACTICE 

the  arc  removed  from  the  ball  by  drilling  a  hole  in  it.  This 
is  equal  to  0.750  inch. 

With  a  feed  for  the  cut-off  tool  of  0.003  inch  per  revolution, 
the  feed  of  the  drill  in  relation  to  the  rotation  of  the  spindle 
is  0.003  X  1.75  =  0.0052  inch.  Then  the  number  of  revolu- 
tions of  the  spindle  equivalent  to  the  time  required  to  drill 
the  cross-hole  is  143.  If  this  work  is  done  on  an  Acme  No.  54 
machine  and  the  speed  is  520  revolutions  per  minute,  it  will 
require  16.5  seconds  to  drill  the  cross-hole.  Adding  the  time 
for  the  idle  movements  —  i  .88  —  gives  a  product  of  one  piece 
in  18.38  seconds,  or  195  pieces  per  hour.  Upon  referring  to 
the  table,  it  will  be  found  that  the  nearest  production  to  this 
for  which  gears  are  provided  is  190  pieces. 

Operation  Requiring  Use  of  Milling  Attachment.  —  The 
cold-rolled  steel  bushing  shown  in  Fig.  31  has  " flats"  milled 
on  the  flange  by  means  of  an  attachment  similar  to  the  one 
shown  in  Fig.  13,  Chapter  VI,  which  is  mounted  on  the  cross- 
slide.  The  end-milling  cutters  are  brought  in  at  the  same 
time  as  the  cut-off  tool  and  work  in  the  " third"  position,  the 
cut-off  tool  severing  the  completed  piece  from  the  bar  in  the 
"fourth"  position.  (Instead  of  using  two  end-milling  cutters 
from  the  side,  this  operation  might  be  done  as  well  with  a 
pair  of  saws  working  from  the  end.)  It  is  evident  from  a  close 
study  of  this  piece,  the  operations  for  which  are  shown  in  Fig.  32, 
that  the  longest  single  cut  lies  between  the  milling  and  form- 
ing operations.  Taking  the  forming  cut  first,  it  will  be  found 
that  the  distance  the  forming  tool  must  travel  is  IQ  inch.  No 
allowance  need  be  made  for  the  tool  to  approach  the  work, 
as  the  diameter  is  finished  by  a  shaving  tool.  The  length  of 
the  forming  tool  is  about  ij  inch,  and  the  smallest  diameter, 
i  inch,  so  that  the  feed  should  not  exceed  0.002  inch.  This 
rate  of  feed  will  require  93  revolutions.  As  the  slab  milling 
attachment  is  carried  on  the  top  face  of  the  cut-off  tool-slide, 
it  can  easily  be  seen  that  the  feed  given  to  the  milling  cutters 
will  be  governed  by  the  feed  used  for  cutting  off.  As  the 
distance  that  the  milling  cutters  must  travel  is  greatly  in  excess 
of  the  travel  of  the  cut-off  tool,  an  accelerating  device  is  used 


USE   OF   MULTIPLE-SPINDLE   TYPE 


297 


Machinery 


Fig.  29.  (A)  Successive  Operations  on  Brass  Thumb-nut.     (B)  Operations 
on  Brass  Knob 

on  the  milling  attachment.     This  increases  the  travel  of  the 
milling  slide  over  the  travel  of  the  cut-off  slide  in  a  ratio  of 


if  to  i. 


With  a  feed  for  the  cut-off  tool  of  0.0025  incri  Per  revolution, 
the  feed  or  rate  of  advance  of  the  milling  cutters  in  relation 


298 


SCREW  MACHINE   PRACTICE 


to  the  revolutions  of  the  spindle  will  be  0.0025  X  1.75  =  0.0043 
inch.  Then  dividing  this  amount  into  the  travel  of  the  slide 
(j|  plus  the  radius  of  the  milling  cutters,  which  are  J  inch  in 
diameter,  plus  0.020  inch  for  clearance)  gives  1.082  inch  travel. 
This  is  equivalent  to  247  revolutions  of  the  spindle. 

This  piece  can  be  most  economically  produced  on  a  No.  54 
machine,  and,  with  a  surface  speed  of  about  95  feet  per  minute, 


Fig.  30.  Example  of  Cross-drilling  on  the  "Acme: 
Automatic  Screw  Machine 


Multiple-spindle 


a  spindle  speed  of  260  revolutions  per  minute  is  obtained.  The 
time  required  to  complete  the  milling  operation  was  found  to 
be  equivalent  to  247  revolutions  of  the  spindle,  or  57  seconds. 
Adding  the  time  for  the  idle  movements  (1.88  second)  gives 
approximately  59  seconds  to  complete  one  piece,  which  is 
equivalent  to  a  product  of  61  pieces  per  hour.  The  nearest 
gears  to  the  product  required  are  those  for  58.5  pieces;  thus 
the  rate  of  production  would  be  decreased  to  this  amount. 


USE  OF  MULTIPLE-SPINDLE  TYPE 


299 


Division  of  Cuts  between  Two  Tools.  —  The  threaded 
bushing  shown  at  A,  Fig.  33,  is  made  from  cold-rolled  steel 
bar,  2 1%  inches  in  diameter.  The  forming  cut  is  rather  heavy, 
so  that  the  production  on  this  piece  can  be  considerably  in- 
creased by  dividing  the  forming  cut  between  two  forming 
tools.  The  first  forming  tool  is  used  for  breaking  down  only 
while  the  second  forming  tool  is  used  to  finish  the  piece  to  the 
desired  shape.  The  greatest  reduction  in  diameter  on  this 
piece  is  yf  mcnj  making  a  rough-forming  travel  of  0.440  inch 
necessary.  Now  the  finish-forming  tool  has  to  travel  prac- 


L 


COLD-ROLLED  STEEL 


Fig.  31.   Bushing  that  is  made  as  indicated  in  Fig  32 

tically  the  same  distance  as  the  rough-forming  tool,  but,  while 
it  does  not  remove  as  much  material,  it  is  operated  by  the 
same  slide  as  the  roughing  tool;  hence,  both  roughing  and 
finishing  cuts  consume  the  same  amount  of  time  and  are  the 
longest  operations. 

Turning  now  to  the  drilling  operation,  it  will  be  found  that 
a  hole  yf  inch  in  diameter  and  2\  inches  deep  has  to  be  drilled. 
This  can  be  divided  between  two  drills,  as  shown  at  the  first 
and  second  spindle  positions,  so  that  the  travel  of  the  main  tool- 
slide  for  drilling  will  be  i|  +  A  inch,  or  a  total  of  1.406  inch. 
The  drills  can  be  operated  successfully  in  this  material  at  a 
feed  of  o.oio  inch  per  revolution,  so  that  140  revolutions  will 
be  required  to  complete  the  drilling  operation.  Figuring  on 
a  feed  of  0.0015  inch  for  the  rough-forming  operation,  and  a 
rise  of  0.445  inch  (0.005  mcn  being  allowed  to  approach  the 
work),  it  requires  296  revolutions  of  the  spindle. 


300 


SCREW   MACHINE   PRACTICE 


The  tool  equipment  used  for  making  the  piece  shown  in  Fig. 
33  is  shown*  in  Fig.  34.  The  first  forming  tool  A  is  held  in  the 
regular  tool-holder,  working  in  the  first  position,  while  the 
second  or  finish-forming  tool  B  is  held  in  a  special  holder, 
attached  to  the  top  face  of  the  forming  slide.  This  holder  is 
provided  with  an  overhanging  arm  in  which  a  set-screw  C 
is  located,  to  enable  the  forming  tool  to  be  held  rigidly  in  place. 
In  making  a  double  tool-holder  of  the  type  illustrated,  it  is 
essential  that  it  be  rigidly  clamped  to  the  tool-slide  and  have 


1ST 

OSITION 


\ 


STRADDLE  MILL 


SHAVE,   FINISH-DRILL  LARGE 
HOLE  AND  FACE 


\ 


REAM  AND  CUT  OFF 


Machinery 


Fig.  32.    Successive  Operations  on  Steel  Bushing  shown  in  Fig.  31 

as  much  bearing  surface  as  is  consistent  with  the  space  avail- 
able. As  a  general  rule,  it  is  advisable,  when  a  holder  is  of  the 
built-up  type,  to  have  the  stock  rotating  toward  the  form  tool 
instead  of  away  from  it.  This  enables  a  much  heavier  cut  to 
be  taken  without  chatter,  as  the  thrust  is  directed  against  the 
tool-slide  instead  of  from  it,  the  latter  action  tending  to  lift 
the  tool.  In  this  case,  however,  the  holder  is  supported  by 
the  top  bracket,  thus  overcoming  the  tendency  of  the  tool 
to  rise.  This  job  also  presents  another  interesting  feature  in 
the  double  or  telescopic  die-holder  D.  This  die-holder,  which 
is  described  in  Chapter  IV  (see  Fig.  38),  can  be  used  for  cutting 


USE   OF    MULTIPLE-SPINDLE   TYPE 


301 


FINISH-FORM  AND  FINISH-DRILL 


CUT  DOUBLE  THREAD 


ROUGH-FORM  AND  DRILL 
LARGE  HOLE  HALF  WAY 


FINISH-FORM  AND  FINISH-DRILL 
LARGE  HOLE 


DRILL  SMALL  HOLE,  SHAVE 
ALL  OVER  AND  FACE 


Machinery 


Fig.  33.   Examples  of  Work  done  on  Multiple- spin  die  Machine 

threads  of  two  different  diameters  and  unequal  pitches,  owing 
to  its  construction.  The  outer  member  of  the  die-holder  is 
spring  controlled  in  its  action,  so  that  it  can  lead  out  in  ad- 
vance of  the  other  part  of  the  holder,  thus  enabling  threads  of 
different  pitches  to  be  cut. 

Another  example  of  work  which  can  be  produced  to  better 
advantage,  by  dividing  the  forming  cuts  between  two  tools, 


302  SCREW   MACHINE   PRACTICE 

is  shown  at  B,  Fig.  33.  Both  forming  tools  are  required  to 
take  long,  heavy  cuts,  so  that  rigidity  is  absolutely  neces- 
sary. In  order  to  keep  the  feed  up  to  a  point  where  a  good 
production  is  possible,  the  arrangement  shown  in  Fig.  35  was 
adopted.  This  consists  in  placing  the  first  forming  tool  in  the 
fourth  position  instead  of  in  the  first,,  as  usual,  and  cutting  off 
the  completed  piece  in  the  third  position.  It  is  evident  that 
the  cut-off  tool  does  not  need  to  be  held  nearly  so  rigidly  as 
a  form  tool,  and  can  be  held  on  an  extension  bracket.  This 
arrangement  allows  the  rough-forming  to  be  done  in  the  fourth 
position  (where  the  stock  is  fed  out),  and  the  finish-forming  in 
the  first  position.  If  the  stock  were  fed  out  in  the  first  posi- 
tion, the  rough-forming  would  have  to  start  at  this  point, 
which  would  not  be  advisable,  as  the  wide  formed  surface 
could  not  be  machined  with  an  extension  tool.  The  arrange- 
ment shown  in  Fig.  35  is  commendable,  in  that  it  obviates 
all  flimsy  construction,  and  enables  the  work  to  be  produced 
much  more  rapidly. 

The  operations  are  as  follows :  In  the  fourth  position  the 
diameter  is  rough-formed,  and  the  large  hole  drilled  part  way 
with  drill  A .  In  the  first  position,  the  forming  cut  is  finished, 
and  the  large  hole  is  drilled  to  the  required  depth  with  drill  B. 
In  the  second  position,  the  small  hole  is  drilled  with  drill  F 
and  the  diameter  finished  all  over  by  a  shaving  tool  D\  the 
end  is  also  faced  with  a  cutter  held  in  the  holder  E  which  is 
attached  to  the  holder  G  carrying  the  drill  F.  In  the  third 
position,  the  hole  is  counterbored  and  taper-reamed,  and  the 
work  is  cut  off. 

Cold-rolled  steel,  as  a  rule,  can  be  worked  at  from  90  to  no 
surface  feet  per  minute.  It  is  found  by  calculation  that  a 
spindle  speed  of  100  revolutions  will  be  about  the  desired  speed 
at  which  to  rotate  the  work.  The  rough-forming  tool  will 
stand  a  very  much  heavier  feed  than  the  finish-forming  tool, 
and,  as  both  tools  have  to  travel  the  same  distance,  it  is  evi- 
dent that  the  finish-forming  operation  will  be  the  one  on  which 
it  will  be  necessary  to  base  our  calculations.  The  form  tool 
is  made  up  of  two  sections  and  the  smallest  diameter  formed 


Fig.  34.  Tool  Equipment  for  Producing  the  Steel  Part  shown  at  A  in  Fig.  33  on 

"Acme  "  Machine 


Fig.  35.  Arrangement  of  Tools  for  Operations  illustrated  at  B  in  Fig.  33 


304  SCREW  MACHINE  PRACTICE 

is  i£J-  inch.  Therefore,  it  would  be  inadvisable  to  use  a  feed 
exceeding  0.0015  inch  per  revolution  of  the  work.  Figuring 
on  a  travel  of  0.350  inch  for  the  finish-forming  tool,  at  the  rate 
of  0.0015  inch  feed  per  revolution,  233  revolutions  will  be 
required  to  complete  this  operation.  As  the  forming  cut  is  the 
longest  single  operation,  we  find  from  this  the  time  to  make 
one  piece.  The  spindle  speed  used  is  100  revolutions  per  min- 
ute, and  the  revolutions  required  for  forming  are  233,  which 
is  equivalent  to  2  minutes  18  seconds ;  adding  the  time  required 
for  the  idle  movements  —  4.6  seconds  —  a  total  of  2  minutes 
23  seconds,  approximately,  will  be  required  to  complete  one 
piece,  or  26  pieces  per  hour. 

Assembling  Parts  in  Screw  Machine.  —  The  assembling  of 
parts  in  the  automatic  screw  machines  is  a  practice  which  is 
not  widely  followed,  but  represents  an  interesting  develop- 
ment. The  examples  to  be  described  include  not  only  the 
assembling  operations,  but  also  the  making  of  the  parts  to  be 
assembled  from  the  same  bar  at  the  same  chucking.  This  not 
only  decreases  the  cost  of  making  the  parts,  but  also  eliminates 
the  necessity  of  handling  them  a  second  time. 

Machining  and  Assembling  a  Bolt  and  Nut.  —  In  Fig.  36 
is  shown  a  small  brass  bolt  and  nut  which  a  jobbing  shop  had 
been  making  for  several  years,  each  part  being  made  on  a  sepa- 
rate machine.  The  assembling  was  done  by  hand,  and  consisted 
of  screwing  the  nuts  on  the  bolts.  These  parts  are  now  made 
in  a  No.  o  Brown  &  Sharpe  automatic  screw  machine  at  the 
same  chucking,  and  assembled  without  rehandling. 

The  most  interesting  feature  of  the  present  method  is  the 
indexing  of  the  turret  twelve  times  during  one  revolution  of 
the  cams;  that  is,  the  turret  makes  two  complete  revolu- 
tions while  the  cams  make  one ;  the  necessity  for  this  will  be 
explained  later.  The  machine  spindle  is  reversed  three  times. 
The  additional  revolving  of  the  turret  and  reversing  of  the 
spindle  are  accomplished  by  the  use  of  extra  tripping  dogs. 

The  method  of  applying  the  circular  tools  and  the  assem- 
bling tool  is  shown  in  Fig.  36.  The  form  tool  A  forms  the 
body  of  the  bolt  and  cuts  off  the  nut,  and  B  is  the  tool  which 


ASSEMBLING  IN  SCREW   MACHINE  305 

cuts  off  the  bolt.  This  latter  tool  is  mounted  on  the  front 
cross-slide.  This  lay-out  requires  but  one  feeding  of  the 
stock  for  both  pieces.  The  turret  tool,  which  is  a  carrier  for 
the  nut,  comes  forward  just  before  the  nut  is  cut  off,  and 
the  spring  chuck  C  closes  over  it.  (The  stock  at  this  point 
is  running  backward.)  The  clutch  finger  D  allows  the  carrier 
C  to  revolve  in  the  holder  E,  thus  preventing  the  nut  from 
turning  in  the  spring  chuck  and  wearing  off  the  corners. 
When  the  nut  is  inserted  in  the  chuck  C,  and  has  been  cut  off, 
the  spindle  is  reversed  to  run  forward,  the  clutch  finger  pre- 
venting the  carrier  from  turning.  This  clutch  also  acts  while 
the  nut  is  being  screwed  on  the  bolt.  The  clutch  is  more 
clearly  shown  in  the  sectional  view  to  the  right.  The  order  of 
operations -is  as  follows: 

Revo-  Hun- 
Order  of  Operations  lutions  dredths 

Feed  stock  to  stop 18  3 

Revolve  turret 18  3 

Drill  —  o.i  78-inch  rise  at  o.oo34-inch  feed v  .  .  53  9 

Revolve  turret 18  3 

Tap  in 12  2 

Tap  out 12  2 

Cut  off  —  o.  145-inch  rise  at  o.ooi  7-inch  feed 83  14 

Revolve  turret  twice  and  bring  carrier  forward (36)  (6) 

Form  with  tool  on  rear  slide  —  o.i3o-inch  rise  at  o.ooo85-inch 

feed: 159  27 

Back  away  form  tool  to  clear  threading  die 12  2 

Revolve  turret  five  times (90)  (15) 

Thread  on 17  3 

Thread  off 17  3 

Revolve  turret 17  3 

Thread  on  nut 12  2 

Reverse  spindle  and  withdraw  turret 12  2 

Cut  off  bolt  —  o.237-inch  rise  at  o.ooig-inch  feed 124  21 

Revolve  turret  twice (36)  (6) 

Clearance 6  i 

Total  revolutions 590  100 

With  a  spindle  speed  of  1474  revolutions  per  minute,  this 
lay-out  gives  a  gross  production  of  1500  pieces  in  ten  hours, 
or  1350  pieces  net.  The  time  required  to  make  and  assemble 
both  pieces  is  24  seconds.  After  the  stock  is  fed  out  to  a  length 
sufficient  to  make  both  pieces,  the  end  is  drilled  and  tapped 
for  the  nut,  which  is  then  inserted  in  the  carrier  and  cut  off. 
The  problem  which  now  arises  is  to  index  the  turret  a  sufficient 
number  of  times  to  bring  the  carrier  into  position  to  screw  the 


306 


SCREW  MACHINE  PRACTICE 


nut  on  the  finished  bolt,  as  soon  as  the  latter  has  been  threaded. 
This  is  successfully  accomplished  by  indexing  the  turret  twice 
while  cutting  off  the  nut,  and  five  times  while  forming  the  bolt. 
The  most  interesting  part  of  the  job  is  the  laying  out  of  the 
cams.  The  usual  set  of  three  cams  is  shown  in  Fig.  37,  the 
outline  of  the  lead  cam  being  shown  as  a  solid  line.  It  will  be 
noticed  that  the  lobe  for  centering  is  omitted  from  the  lead 
cam.  This  is  done  because  of  the  shallow  depth  of  the  hole 


Machinery 


Fig.  36.   Method  of  Applying  the  Circular  Tools;   the  Carrier  or  Assembling 
Tool,  and  Nut  and  Bolt  to  be  made  and  Assembled 

to  be  drilled,  and  also  because  the  work  is  not  required  to  be 
very  accurate. 

The  lobe  which  operates  the  carrier  when  gripping  the  nut 
is  shown  from  28  to  36  on  the  lead  cam,  Careful  calculations 
are  necessary  to  determine  the  exact  position  of  this  lobe,  so 
that  the  carrier  will  grip  the  nut  before  it  is  cut  off.  The 
method  used  to  determine  the  position  of  this  lobe  is  as  fol- 
lows: During  the  time  from  22  to  28,  which  is  equal  to  36 
revolutions  of  the  spindle,  the  cut-off  tool  has  advanced  at  the 
rate  of  0.0019  inch  per  revolution,  or  36  X  0.0019  =  0.0684  mcn- 
The  diameter  of  the  stock  across  the  corners  is  0.432  inch,  and 
the  diameter  of  the  drilled  hole  is  0.125  inch.  Then  the  thick- 
ness of  the  wall  on  each  side  of  the  hole  when  the  carrier  ad- 


vances   on   the  work  = 


0.432  —  (0.0684  X  2)  —  0.125 


=  0.085 


inch,  which  is  great  enough  to  prevent  the  nut  from  breaking 
off  when  the  carrier  closes  over  it. 


ASSEMBLING  IN  SCREW  MACHINE 


307 


The  hook-shaped  lobe  from  74  to  76  threads  the  nut  on 
the  bolt,  and  the  sudden  drop  pulls  the  carrier  off  the  nut. 
The  spindle  is  then  reversed,  so  that  it  will  be  rotating  in  the 
correct  direction  to  cut  off  the  finished  piece.  The  portion  of 
the  cam  surfaces  from  99  to  o  allows  the  cut-off  tool  to  drop 
back  and  clear  the  stock  before  it  is  fed  out  for  the  next  piece. 


RILL  THE  NUT 


0.237    CUT  OFF  BOLT       / 

FRONT  SLIDE  /       /  / 

(R.T.   TWICE)        /        /    / 


36 

RM    0.130   BACK   SLIDE 
(R.T.    5   TIMES) 

Machinery 


Fig.  37.   Cams  used  for  Making  and  Assembling  Nuts  and  Bolts 

Assembling  by  Means  of  Spinning  Tool.  —  An  assembling 
operation  which  is  a  little  more  difficult  than  that  previously 
described  is  shown  at  A,  Fig.  38.  This  operation  was  accom- 
plished in  a  No.  2  Brown  &  Sharpe  automatic  screw  machine 
and  consists  in  making  and  assembling  the  socket  joint  a  and 
grooved  roller  b.  When  in  use,  this  grooved  roller  rides  between 
two  tracks  as  shown  at  A,  and  the  ball  part  rotates  freely  in 
the  socket  joint  a.  The  work  was  not  required  to  be  held  to 


308 


SCREW  MACHINE  PRACTICE 


very  close  limits,  and  the  milling  and  drilling,  as  shown  at  B, 
were  done  in  separate  operations. 

In  setting-up  the  machine  for  making  the  pieces  a  and  b, 
the  stock  is  first  fed  out  by  hand  to  the  length  shown  at  A, 
Fig.  39,  where  the  bar  is  faced  off,  and  the  grooved  roller 


ADE  FROM  %  SCREW  STOCK 


Fig.  38.   Pieces  to  be  Made  and  Assembled 

formed ;  the  stock  is  then  fed  out  to  the  length  shown  at  B 
where  the  grooved  roller  is  cut  off.  When  in  this  position, 
the  slotting  arm  descends,  carrying  the  pick-up  shown  at  C  in 
Fig.  40,  which  grips  the  grooved  pulley,  and  after  it  is  cut 
off  lifts  it  out  of  the  way  ready  to  be  brought  back,  when  it 


Machinery.N.Y. 


Fig.  39.   Positions  of  the  Stock  for  the  Various  Operations 

is  to  be  assembled  in  the  socket  joint.  While  the  stock  is 
in  the  position  shown  at  B  (Fig.  39),  the  hole  is  drilled  and 
reamed.  The  reamer,  shown  at  A  in  Fig.  40,  is  so  shaped 
that  it  makes  a  correct  seat  for  the  ball  on  the  grooved  roller. 

The  tapered  part  a  (Fig.  39)  of  the  socket  joint  is  formed 
with  a  box-tool  after  the  hole  has  been  drilled  and  reamed. 


ASSEMBLING  IN   SCREW   MACHINE  309 

When  this  operation  is  finished,  the  slotting  arm  is  brought 
down,  carrying  the  grooved  roller,  and  the  spring  stop  B, 
Fig.  40,  which  is  held  in  the  turret,  and  forces  the  roller  into 
the  socket  joint.  The  spring  stop  remains  stationary  in  this 
position,  as  does  the  pick-up,  while  the  spinning  tool  b,  shown 
in  Fig.  39,  which  is  held  rigidly  to  the  rear  cross-slide,  is  ad- 
vanced and  turns  the  nose  of  the  joint  over  the  ball,  thus  as- 
sembling the  two  parts.  When  this  is  accomplished,  the  spring 
stop  is  dropped  back  and  the  stock  fed  out  against  it.  The 
stock  is  now  in  the  position  as  shown  at  C,  where  the  completed 
joint  is  cut  off  and  the  next  roller  formed  to  shape,  as  shown 
by  the  dotted  outline,  which  would  leave  the  stock  in  the  same 
position  as  at  A.  The  operations  for  making  and  assembling 
these  two  pieces  are  as  follows : 

Revo-  Hun- 
Order  of  Operations  lutions        dredths 

Feed  stock  to  stop 23  3 

Cut  off  —  0.3 75-inch  rise  at  0.002 i-inch  feed 177  23 

Cut  off  and  form  —  o.o4o-inch  rise  at  o.ooi 2-inch  feed 32  4 

Clearance  to  bring  down  slotting  arm  while  cutting  off  piece, 

take  hold  of  piece  and  return  slotting  arm 7  i 

Center —  o.2oo-inch  rise  at  0.0051 -inch  feed 39  5 

Revolve  turret 23  3 

Turn  with  box- tool —  0.3  75-inch  rise  at  o.oo6-inch  feed 62  8 

Revolve  turret 23  3 

Drill  —  o.387-inch  rise  at  o.oo46-inch  feed 85  n 

Revolve  turret 23  3 

Ream  —  o.387-inch  rise  at  o.oo82-inch  feed 47  6 

Revolve  turret  and  bring  down  slotting  arm  with  piece 23  3 

Push  in  piece  with  holder  B,  held  in  slotting  arm  (Fig.  40) ...  (23)  (3) 
Spin  over  end  with  spinning  tool  held  on  rear  slide  —  0.125- 
inch  rise  at  o.oo54-inch  feed 23  3 

Withdraw  holder  and  feed  stock  to  stop 31  4 

Cut  off  and  form  —  o.27o-inch  rise  at  o.oo2-inch  feed 131  17 

Revolve  turret 23  3 

Total  revolutions 772  100 

With  a  spindle  speed  of  421  revolutions  per  minute,  it 
requires  no  seconds  to  make  one  piece,  which  gives  a  gross 
production  of  327  pieces  in  ten  hours.  The  cams  for  making 
and  assembling  the  pieces  a  and  6,  Fig.  38,  are  shown  in  Fig. 
41,  where  the  lobes  for  performing  the  various  operations  are 
clearly  outlined. 

Assembling  a  Roller  on  its  Bearing.  —  Another  operation 
requiring  assembling  is  shown  in  Fig.  42.  A  No.  2  Brown  & 


3io 


SCREW   MACHINE   PRACTICE 


Sharpe  automatic  screw  machine  was  used.  This  part  is  made 
up  of  a  stud  a,  on  which  turns  the  roller  b,  held  in  place  by  the 
washer  c,  the  latter  being  pressed  on  the  stud.  The  part  is 
shown  disassembled  at  B.  There  are  two  unusual  operations 
to  be  performed.  The  first  is  to  ream  a  large  hole  behind  a 
small  one,  and  the  second  is  to  cut  off  three  times,  requiring 
the  stock  to  be  fed  out  three  times  for  the  completion  of  each 
assembled  part. 

In  operation,  the  stock  is  first  fed  out  to  the  length  shown 
at  A  in  Fig.  43,  where  the  hole  is  centered,  drilled,  and  the 
washer  shown  in  section  at  a  is  reamed  to  0.375  inch  in 


COIL  SPRINQ 


TOOL  STEEL  SPRING  TEMPERED 


Machinery,  N.Y. 


Fig.  40.   Reamer,  Assembling  Tool,  and  Pick-up 

diameter.  The  remainder  of  the  hole,  which  is  in  that  part 
of  the  stock  that  will  form  the  roller,  is  bored  with  a 
recessing  tool  to  0.380  inch.  Meanwhile  the  circular  form 
tool  b  has  turned  the  hub  c  to  0.377  inch  in  diameter,  and 
also  formed  the  groove  in  the  roller.  The  form  tool  leaves 
sufficient  stock  around  the  bottom  of  the  hole  to  hold  the 
parts  together. 

Before  cutting  off  the  washer,  the  special  tool  shown  at  B 
comes  forward  and  enters  f  inch  into  the  hole.  The  pilot  of 
this  tool  is  slotted  and  spring-tempered,  so  that  it  will  take 
hold  of  the  washer  when  it  is  cut  off.  When  the  washer  is 
separated  from  the  bar,  the  cut-off  tool  drops  back  and  the 
stock  is  fed  forward  sufficiently  to  allow  the  roller  to  be  cut 
off.  The  pilot  tool  has  now  entered  the  hole  of  the  roller  as 
seen  at  B,  which  also  shows  the  relative  position  of  the  washer. 


ASSEMBLING  IN  SCREW  MACHINE  311 

This  pilot  tool  is  also  used  as  the  stop,  the  stock  being  fed 
against  the  face  d. 

The  pilot,  holding  both  the  roller  and  the  washer,  now 
moves  forward  until  the  end  comes  in  contact  with  the  stud 
at  e,  when  the  turret  still  advances  sufficiently  to  push  the 
roller  onto  the  stud,  and  also  to  press  the  washer  onto  the  end, 
thus  holding  the  roller  in  place.  In  the  meantime,  the  pi- 
lot has  been  held  against  the  end  of  the  stud  by  the  coil 
spring  /.  The  work  is  now  fed  forward  to  the  over-all  length, 
and  cut  off  as  shown  at  C.  Provision  is  made  for  the  slight 
burr  which  is  left  around  the  edge  of  the  hole  when  the  roller 
is  cut  off,  by  cutting  a  groove  g  in  the  stud,  as  shown  at  A. 
The  outside  diameter  of  the  washer  is  turned  with  a  box-tool, 
which  obviates  the  necessity  of  using  an  extremely  wide  form- 
ing tool.  The  order  of  operations  is  as  follows : 

Revo-  Hun- 
Order  of  Operations  lutions  dredths 

Feed  stock  to  stop 27  2 

Revolve  the  turret •      34  i\ 

Turn  and  center  with  box-tool  —  o.i45-inch  rise  at  0.0054- 

inch  feed 27  2 

Form  —  o.35o-inch  rise  at  o.ooi-inch  feed (350)  (25) 

Revolve  the  turret 41  3 

Drill —  o.56i-inch  rise  at  o.oo45-inch  feed 125  9 

Revolve  the  turret 42  3 

Ream  —  o.i45-inch  rise  at  o.oo52-inch  feed 28  2 

Revolve  the  turret 41  3 

Recess — front  cross-slide  cam,  o.on-inch  rise  at  o.ooi-inch 

feed 14  i 

Recess  —  lead  cam,  o.26o-inch  rise  at  o.oo74-inch  feed 35  2\ 

Revolve  the  turret 42  3 

Cut  off  the  washer  —  o.36o-inch  rise  at  o.oo2-inch  feed 180  13 

Take  hold  of  washer  with  pilot 

Clearance 14  i 

Feed  stock  against  pilot  holder 27  2 

Cut  off  roller  —  o.554-inch  rise  at  o.oo2-inch  feed 277  20 

Clearance 28  2 

Push  on  roller  and  washer  —  o.375-inch  rise 42  3 

Revolve  the  turret 42  3 

Feed  stock  to  stop 28  2 

Cut  off  finished  piece  —  0.5 54-inch  rise  at  o.oo2-inch  feed 277  20 

Clearance 14  i 

Total ^385  loo 

With  a  spindle  speed  of  277  revolutions  per  minute,  it 
requires  300  seconds  to  complete  one  assembled  part,  which 
gives  a  gross  output  of  120  pieces  in  ten  hours.  In  this  case, 


312 


SCREW  MACHINE  PRACTICE 


REVOLVE  TURRET 
4  DESCEND  SLOTTING 
ARM  WHM.E  CUTTING 
OFF 


Machinery.  N.Y. 


Fig.  41.   Cams  used  for  Making  and  Assembling  a  Grooved  Roller  and 
Socket  Joint 


PRESS  FIT 
'  LOOSE  FIT 


:I;  _ 


Machinery 


Fig.  42.   The  Assembled  Part  and  its  Details 


Machinery 


Fig.  43.   Positions  of  Stock  for  the  Various  Operations 


ASSEMBLING  IN   SCREW  MACHINE 


313 


a  combination  box-tool  and  center  tool  was  necessary,  as  the 
turret  was  filled  with  tools.  Referring  to  the  lay-out  of  the 
cams  shown  in  Fig.  44,  it  will  be  seen  that  there  are  a  number 
of  short  lobes  on  the  lead  cam.  These  lobes,  when  made 
accurately,  will  work  just  as  well  as  the  longer  ones,  because 
the  cam  is  turning  very  slowly.  The  front-slide  cam  from  26^ 


LEAD 

FRONT 

REAR 


Machinery 


Fig.  44.   Lay-out  of  the  Cams  for  Machining  and  Assembling  Operations 

to  27^  feeds  the  recessing  tool  in  at  right  angles  to  the  spindle, 
and  from  27^  to  30  is  a  dwell,  while  the  .recessing  tool  is  fed 
forward  by  the  lead  cam.  The  front  slide  drops  back  a  little 
ahead  of  30,  so  as  to  release  the  recessing  tool,  before  it  is 
withdrawn  by  the  turret.  From  33  to  46,  the  front  cam  ac- 
tuates the  cut-off  tool,  separating  the  washer  from  the  bar, 
and,  after  dropping  back  enough  at  46  to  allow  the  roller  to  be 
fed  out,  it  again  advances  and  cuts  off  the  roller.  After  again 


314  SCREW  MACHINE  PRACTICE 

feeding  the  stock,  the  finished  part  is  cut  off  by  the  lobe  from 

79  to  99- 
The  dwell  on  the  lead  cam  which  follows  the  recessing  lobe 

keeps  the  spring  pilot  in  the  hole  of  the  washer  while  it  is  being 
cut  off.  From  47  to  49,  the  stock  is  fed  forward  preparatory 
to  cutting  off  the  roller.  The  rise  from  71  to  74,  which  pushes 
the.  roller  and  washer  onto  the  stud,  was  not  made  when  the 
job  was  first  set  up,  as  it  was  a  case  of  cut-and-try,  in  order 
to  obtain  the  proper  advance.  The  shape  of  the  curve  shown 
in  the  illustration  was  finally  arrived  at  and  was  successful. 
When  the  stock  is  fed  (77  to  79  on  the  cam),  it  reaches  the 
length  shown  at  C  in  Fig.  43,  and  when  it  is  again  fed  (o  to  2 
on  the  cam),  it  reaches  the  length  shown  at  A.  The  weight 
of  the  piece  causes  it  to  drop  before  the  cut-off  tool  has  reached 
point  99,  so  that  no  interference  occurs  when  revolving  from 
one  stop  to  the  other. 

It  might  be  well  to  give  the  reason  why  one  stop  could  not 
be  used  for  these  last  two  feeding  movements  of  the  stock, 
thus  allowing  space  in  the  turret  for  a  centering  tool  instead  of 
using  the  combination  box-tool  and  center.  The  reason  this 
could  not  be  done  is  that  the  difference  in  the  length  between 
the  two  feeding  movements  is  so  great  that  the  cam  from 
77  to  79  would  have  to  be  cut  very  much  lower  than  it  is  from 
o  to  2 ,  and,  in  rising  from  the  low  to  the  higher  point  of  the 
cam,  the  stop  in  the  turret  would  strike  the  work  before  it  was 
cut  off ;  of  course,  cam  space  could  be  allowed  to  prevent  this, 
but  it  would  mean  lost  time. 

Thread  Rolling  in  the  Screw  Machine.  —  The  formation  of 
threads  by  rolling  is  effected  by  hardened  rolls  or  dies  having 
threads  or  ridges  which  roll  grooves  into  the  blank  and  raise 
enough  material  above  the  surface  of  the  blank  to  form  a  thread. 
When  threads  are  rolled  in  the  automatic  screw  machine, 
the  tool  used  is  in  the  form  of  a  disk  having  a  threaded 
periphery  and  mounted  so  as  to  revolve  freely  when  forced 
against  the  blank  to  be  threaded.  Thread  rolling  is  done  in 
automatic  screw  machines,  when  a  thread  is  required  behind 
a  shoulder  where  it  would  be  impossible  to  cut  it  with  a  die. 


THREAD  ROLLING  315 

In  this  way,  a  second  operation  on  the  work  is  obviated.  The 
roll  used  for  forming  the  thread  should  be  large  enough  in 
diameter  to  turn  freely  on  the  pin  on  which  it  is  mounted. 
The  thread  on  the  roll  should  be  the  opposite  hand  to  that 
which  is  to  be  produced  on  the  work ;  that  is,  if  the  thread 
required  on  the  work  is  to  be  right-hand,  then  the  roll  should 
be  left-hand,  and  vice  versa.  For  rolling  a  right-hand  thread, 
the  work  should  revolve  in  the  same  direction  as  when  a  thread 
is  cut  in  the  lathe.  Whenever  practicable,  the  roll  should  pass 
under  the  work.  The  roll-holder  should  have  a  vertical  adjust- 
ment so  that  the  roll  can  be  set  to  the  proper  height. 

Thread  rolling  in  automatic  screw  machine  practice  is  gen- 
erally only  applied  to  brass  and  similar  materials,  owing  to 
the  difficulty  of  securing  a  roll  that  will  withstand  the  severe 
service  incident  to  rolling  threads  in  harder  metals.  Thread 
rolls  for  steel  work,  however,  have  given  fairly  good  results, 
when  made  of  chrome-nickel  steel  containing  from  0.15  to 
0.20  per  cent  of  carbon.  Thread  rolls  for  brass  and  similar 
materials  should  be  made  from  3-per  cent  nickel  steel  contain- 
ing about  o.i  2  per  cent  of  carbon.  The  heat- treatment  recom- 
mended is  as  follows :  Carburize  six  hours  in  straight  coarse 
bone  (not  bone  dust),  heating  to  a  temperature  of  1600  de- 
grees F.,  and  allow  the  rolls  to  cool  in  the  pots.  Then  heat  to 
1600  degrees  F.  and  quench  in  oil.  Reheat  to  1400  degrees  F. 
and  quench  in  water,  after  which  draw  the  temper  to  400 
degrees  F.  in  oil.  The  following  information  applies  to  the 
rolling  of  threads  in  brass  and  other  soft  materials,  and  is 
largely  based  upon  experiments  made  by  the  Brown  &  Sharpe 
Mfg.  Co.  . 

Obtaining  the  Blank  Diameter.  —  As  a  rule,  the  diameter 
of  the  blank  for  brass  should  be  approximately  equal  to  the 
pitch  diameter.  When  rolling  a  U.  S.  standard  thread,  the 
diameter  of  the  blank  should  be  slightly  less  than  the  pitch 
diameter  of  the  thread,  because  of  the  impracticability  of  using 
a  thread  roll  with  a  flat  top.  If  the  threads  on  the  roll  are  not 
made  sharp  at  the  top,  considerably  more  pressure  will  be 
required  to  force  the  roll  into  the  work,  and  it  will  not  produce 


316  SCREW  MACHINE  PRACTICE 

as  smooth  and  perfect  a  thread.  Therefore,  all  thread  rolls, 
whether  for  forming  a  sharp  V  or  a  U.  S.  standard  thread,  are 
made  with  a  sharp  V,  top  and  bottom.  It  is  not  necessary 
to  make  the  bottom  of  the  thread  on  the  roll  sharp,  but  there 
would  be  no  advantage  in  having  it  flat,  as  the  outside  di- 
ameter of  the  screw  is  governed  by  the  diameter  of  the  blank. 
The  shape  of  the  thread  produced  by  a  thread  roll,  when  the 
U.  S.  standard  form  is  required,  is  shown  in  Fig.  46  (central 
illustration).  The  pitch  diameter  B  is  the  same  as  the  pitch 
diameter  of  the  U.  S.  standard  form,  Fig.  45.  The  root  di- 
ameter C,  however,  is  less  than  the  root  diameter  A  of  the  U.  S. 


Figs.  45,  46,  and  47.  Dimensions  involved  in  Calculating  Blank  Diam- 
eters for  Thread  Rolling 

standard  thread.  The  approximate  diameter  of  the  blank 
can  be  found  by  the  following  formula,  in  which  D  =  diameter 
of  the  blank ;  B  =  pitch  diameter  of  the  screw ;  F  =  depth 
of  U.  S.  standard  thread  =  0.6495  P  '• 

D  =  B  -  i  F. 

The  pitch  diameter  B  =  d  —  F,  in  which  d  =  nominal  ex- 
ternal diameter  of  the  screw. 

When  rolling  a  thread  having  a  sharp  V-form,  the  pitch 
diameter  £,  Fig.  47,  can  be  used  as  the  approximate  diameter 
of  the  blank.  The  pitch  diameter  for  a  V-thread  is  found  by 
the  formula  :  E  =  d  —  H,  in  which  H  =  0.866  p.  The  cor- 
rect diameter  of  the  blank,  in  any  case,  must  be  determined 
by  experiments,  owing  to  variations  in  the  hardness  of  differ- 
ent materials.  It  is  a  simple  matter,  however,  in  the  automatic 
screw  machine,  to  reduce  or  increase  the  diameter  of  the  blank 
so  as  to  obtain  a  screw  of  the  required  diameter. 


THREAD  ROLLING  317 

Size  of  the  Thread  Roll.  —  The  best  results  are  obtained  by 
using  a  thread  roll  with  a  single  thread,  but,  when  the  piece 
to  be  rolled  is  less  than  f  inch  in  diameter,  it  is  necessary  to 
make  the  roll  with  a  multiple  thread,  because  the  diameter 
of  the  roll  must  then  be  made  twice  the  diameter  of  the  blank. 
The  Brown  &  Sharpe  Mfg.  Co.  has  found  that  the  pitch  di- 
ameter of  the  roll  should  not  be  an  exact  multiple  of  the  pitch 
diameter  of  the  finished  piece,  but  slightly  less.  The  pitch 
diameter  of  the  roll  for  a  U.  S.  standard  thread  can  be  found 
by  the  following  formula,  in  which  K  =  pitch  diameter  of  roll ; 
N  =  approximate  ratio  between  pitch  diameter  of  roll  and 
pitch  diameter  of  piece  to  be  threaded ;  D  =  outside  diameter 
of  blank ;  G  =  depth  of  thread : 

K  =  NX(D-±G). 

For  a  sharp  V-thread,  the  root,  pitch,  and  outside  diameters 
of  the  roll  are  found  by  the  following  formulas,  in  which 
DI  =  pitch  diameter  of  thread  roll ;  D2  =  root  diameter  of 
thread  roll ;  D$  =  outside  diameter  of  thread  roll ;  N  =  ap- 
proximate ratio  between  pitch  diameter  of  roll  and  pitch 
diameter  of  piece  to  be  threaded ;  E  =  pitch  diameter  of  thread 
or  diameter  of  blank ;  H  =  depth  of  thread  =  0.866  p : 

D1  =  NX(E-^H);        D^D.-H;        D3=  D,+  H. 

The  thread  rolls  used  by  the  National-Acme  Mfg.  Co.  are 
made  from  ij  to  2j  inches  in  diameter  and  sometimes  larger, 
multiple  threads  being  used  when  the  work  is  smaller  than 
the  outside  diameter  of  the  thread  roll.  Assuming  that 
DI  =  outside  diameter  of  thread  roll ;  n  =  number  of  " starts" 
or  threads  on  the  roll ;  d  =  outside  diameter  of  part  to  be 
threaded  (diameter  after  completion  of  thread) ;  G  =  depth 
of  thread ;  then : 

Di=nX(d-  1.25  G). 

When  making  a  thread  roll,  the  outside  diameter  is  turned 
to  the  size  required,  and  the  end  should  be  beveled  to  an  angle 
of  45  degrees  (as  shown  to  the  right  in  Fig.  48),  to  prevent 
the  thread  at  the  end  from  chipping  or  breaking  out.  Thread 
rolls  are  usually  lapped  after  hardening,  in  order  to  obtain  a 
smooth  finish  on  the  threads.  This  may  be  done  by  mounting 


SCREW  MACHINE  PRACTICE 


the  roll  on  an  arbor  and  rotating  it  while  the  threads  are 
lapped,  by  using  a  piece  of  hard  wood  charged  with  some  fine 
abrasive  and  oil. 

Preparation  of  Work  for  Thread  Rolling.  —  In  most  cases, 
that  part  of  the  work  on  which  a  thread  is  to  be  rolled  can  be 
turned  by  a  formed  tool.  The  thread  to  be  rolled  is  usually 
at  the  rear  of  a  shoulder  and,  in  such  cases,  it  is  desirable 
to  use  a  formed  tool  of  such  a  shape  that  it  will  cut  an  annular 
groove  next  to  the  shoulder,  as  shown  at  A  in  the  view  to  the 
left  of  Fig.  48.  The  diameter  at  B  should  also  be  reduced  at 
the  point  where  the  work  is  to  be  cut  off  from  the  bar  of  stock. 
The  angle  a  should  be  45  degrees,  and  the  distance  C  equal 


H G— -H 


-+\P  p-PITCH 


\L 

''   V 

s^  — 

V 

f 
i 

j 

\ 

i 

—  1 

I 

Fig.  48.   Preparing  a  Part  for  Thread  Rolling — Thread  Roll  with  a 
Double  Thread 

to  at  least  half  the  single  depth  of  the  thread,  so  that  the  part 
B  will  be  slightly  smaller  than  the  root  diameter  of  the  threaded 
part.  The  distance  E  should  be  made  equal  to  C  and  dimen- 
sion F  equal  to  at  least  the  pitch  of  the  thread. 

Application  of  Thread  Roll  to  Work.  —  Thread  rolls,  like 
knurls,  are  presented  to  the  work  either  radially  or  tangen- 
tially.  The  method  of  holding  and  applying  the  roll  is  gov- 
erned, in  many  cases,  by  the  relation  that  the  thread  rolling 
operation  bears  to  other  machining  operations.  The  de- 
sign of  the  holder  for  the  thread  roll  is  also  governed  to  some 
extent  by  the  type  of  screw  machine  for  which  the  holder  is 
intended.  Several  types  of  holders  adapted  to  different  con- 
ditions and  different  designs  of  machines  will  be  described. 


THREAD  ROLLING 


319 


Thread  Roll  Applied  to  Top  Side  of  Work. —  The  holder 
shown  in  Fig.  49  is  intended  for  a  Brown  &  Sharpe  machine. 
It  is  attached  to  the  cross-slide  and  operates  tangentially  on 
the  top  side  of  the  work.  When  no  other  tool  is  operating  at 
the  same  time  as  the  thread  roll  and  there  are  no  chips  to 
interfere  with  the  thread  rolling  operation,  the  roll  can  be 
held  more  rigidly  than  by  passing  it  under  the  work  instead 
of  over  it.  When  the  roll  is  fed  over  the  work,  there  is  a  ten- 


THREAD  ROLL-HOLDER 


THREAD  ROLL 


CIRCULAR  CUT-OFF  TOOL 


Machinery 


Fig.  49.   Application  of  Thread  Roll  to  Top  Side  of  Work 

dency  to  raise  the  cross-slide,  whereas,  when  the  roll  operates 
on  the  under  side  of  the  work,  the  pressure  is  downward  and, 
consequently,  the  holder  is  more  rigidly  supported.  The 
thread  roll  shown  in  Fig.  49  rotates  on  a  pin  and  is  inserted 
in  a  slot  cut  in  the  end  of  the  holder.  The  roll  should  closely 
fit  both  the  pin  and  the  slot  in  the  holder,  because  any  lost 
motion  would  result  in  marring  the  thread.  The  set-screw 
at  the  rear  of  the  holder  is  used  for  setting  the  roll  to  the  proper 
depth.  The  cutting-off  tool  is  located  back  of  the  thread  roll 


320 


SCREW  MACHINE  PRACTICE 


so  that  the  work  will  be  severed  from  the  bar  before  the  roll 
returns.  The  roll  should  be  moved  in  to  within  about  o.oio 
inch  from  the  work  on  the  quick  rise  of  the  cam,  and  then  be 
fed  in  until  the  roll  is  directly  over  the  center  of  the  work,  at 
a  feed  which  usually  varies  from  about  0.002  to  0.004  inch  per 
revolution  of  the  work.  The  roll  should  then  be  moved  past 
the  work  rapidly,  thus  bringing  the  cutting-off  tool  into 
position. 

Thread  Roll  Applied  to  Under  Side  of  Work.  —  The  thread- 
roll  holder  shown  in  Fig.  50  is  attached  to  the  cross-slide,  and 
the  roll  is  so  located  that  it  passes  beneath  the  work  when 


CIRCULAR  CUT-OFF  TOOL 


CROSS-SLIDE 


Machinery,  Jf.Y. 


Fig.  50.   Holder  used  when  the  Thread  Roll  is  passed  under  the  Work 

forming  a  thread.  The  set-screw  A  bears  against  the  cross- 
slide  and  is  used  for  adjusting  the  roll  to  the  proper  depth  as 
well  as  for  supporting  the  holder.  This  type  of  holder  may  be 
used  when  no  other  tool  is  operating  on  the  work  at  the  same 
time  and  there  are  no  chips  to  interfere  with  the  thread  rolling 
operation.  The  cutting-off  tool  located  back  of  the  roll 
severs  the  work  after  the  thread  is  finished,  so  that  the  roll 
does  not  come  into  contact  with  the  thread  on  its  return 
movement. 

Swing  Tool  for  Thread  Rolling.  —  When  the  thread  roll 
cannot  be  carried  on  the  cross-slide  of  a  Brown  &  Sharpe 
machine,  a  swing  type  of  tool,  similar  to  the  design  shown  in 


THREAD   ROLLING 


32I 


Fig.  51,  is  employed.  For  instance,  if  it  were  necessary  to 
feed  in  the  cut-off  or  form  tool  more  than  once  on  the  same 
piece,  a  swing  holder  should  be  used  in  preference  to  the  cross- 
slide  type.  The  swing  holder  operates  upon  the  same  prin- 
ciple as  an  ordinary  swing  tool  for  turning.  There  is  a  swinging 
arm  which  carries  the  roll  and  which  is  moved  inward,  for 
bringing  the  roll  into  contact  with  the  work,  by  means  of  a 
raising  plate  attached  to  the  cross-slide  which  engages  the  set- 
screw  located  at  the  end  of  the  swinging  arm.  The  shank 
of  the  holder  is  inserted  in  a  hole  in  the  turret.  If  the  length 
of  the  work  exceeds  about  2\  times  its  diameter,  the 


Fig.  51.   Swing  Holder  for  Thread  Rolling 

swing-roll  holder  should  be  equipped  with  a  support.  A 
hole  is  drilled  through  the  shank  of  the  holder  and  a  set- 
screw  is  provided  for  holding  the  supporting  member.  The 
method  of  applying  this  support  is  governed  by  the  shape  of 
the  work. 

Cleveland  Thread-rolling  Attachment.  —  The  thread-rolling 
attachment  shown  in  Fig.  52  is  similar  in  construction  to  the 
independent  cut-off  attachment  used  on  the  Cleveland  auto- 
matic, except  that  the  roll  holder  and  thread  roll  replace  the 
cut-off  blade  and  holder.  The  thread  roll  A  rotates  on  a  pin 
B,  and  arm  C  is  pivoted  at  the  center  and  operated  by  a  cam 
attached  to  a  disk  on  the  camshaft  seen  at  the  rear.  This  cam 


322  SCREW  MACHINE   PRACTICE 

may  be  adjusted  according  to  requirements.  The  roller  at 
the  rear  end  of  arm  C,  which  engages  the  cam,  is  mounted  on 
an  eccentric  stud  so  that  fine  adjustments  may  be  obtained  for 
the  thread  roll. 

Acme  Thread-roll  Holder.  —  A  type  of  thread-roll  holder 
commonly  used  on  the  Acme  multiple-spindle  automatic 
screw  machine  is  shown  in  Fig.  53.  The  thread  roll  is 
presented  radially  to  the  work  and  slightly  off  center,  so 
as  to  permit  the  tool  to  spring  away  a  certain  amount  to 


Fig.  52.  Thread-rolling  Attachment  Applied  to  Cleveland  Automatic 

follow  the  curvature  of  the  stock.  This  makes  it  unneces- 
sary to  set  the  tool  absolutely  correct  in  regard  to  position 
for  depth  of  thread.  The  spring  of  the  tool  should  not  be 
excessive,  but  just  enough  to  relieve  the  strain  which  would 
be  imposed  on  the  tool  if  it  were  in  a  central  position.  Fig. 
54  illustrates  how  a  thread  roll  and  holder  of  similar  form  is 
applied  to  the  work  on  an  Acme  machine.  The  thread  roll  is 
held  in  a  side-working  slide  in  the  third  position  and,  in 
this  particular  case,  a  shaving  tool  operates  in  the  second 
position. 


CUTTING  HELICAL   GEARS 


323 


Cutting  Helical  Gears  in  Screw  Machine. —  The  ribbon 
spools  of  a  certain  typewriter  are  rotated  by  a  system  of  shafts 
and  gearing,  which  includes  a  pair  of  small  spiral  or  helical 
gears.  These  gears  formerly  were  cut  on  small  hand-operated 
gear-cutting  machines  of  special  design,  which  performed  the 
operation  in  the  same  way  that  helical  gears  are  cut  in  a  milling 
machine ;  that  is,  the  blank  was  fed  forward  and  rotated  at  the 
same  time  under  a  revolving  formed  cutter.  It  was  then 
returned  to  the  starting  position  again,  indexed  and  fed  for- 
ward for  a  second  cut  —  and  so  on  until  all  the  teeth  were 
formed.  The  tools  and  operations  employed  for  doing  this 
work  on  a  Brown  &  Sharpe  automatic  screw  machine  will  be 


Machinery 


Fig.  53.   Thread  Roll  used  on  Acme  Multiple-spindle  Automatic   ' 

described.  The  effectiveness,  rapidity,  and  comparative  sim- 
plicity of  the  mechanism  indicate  the  versatility  of  the  auto- 
matic screw  machine. 

Helical  Gear  Generating  Tool.  —  The  tool  used  for  generat- 
ing the  teeth  of  the  helical  gears  is  shown  in  Fig.  55.  When  this 
tool  comes  into  action,  the  blank  has  been  formed  in  the  ma- 
chine as  shown  at  C  in  Fig.  56.  The  hole  has  been  drilled  and 
reamed  and  the  outside  diameter  formed  to  the  required 
dimensions.  When  the  tool  is  brought  up  to  the  work,  the 
three-cornered  driving  center  G  enters  the  drilled  hole,  and  is 
thereby  caused  to  revolve  with  the  blank.  As  it  is  screwed 
firmly  into  the  long  driving  gear  H  (Fig.  55)  the  latter  is  also 
set  in  motion  in  unison  with  the  spindle  of  the  machine.  Gear 
H  has  helical  teeth  cut  on  it  engaging  mating  teeth  in  helical 
gear  /,  which  is  mounted  on  a  short  horizontal  shaft  having 


324 


SCREW  MACHINE  PRACTICE 


spur  gear  K  keyed  to  it  at  the  rear  end.  This  gear,  through 
a  large  idler  L,  drives  gear  M,  which  is  keyed  to  the  cutter 
spindle  S.  Cutter  N  mounted  on  the  spindle  has  the  form  of 
a  helical  gear  properly  cut  to  mesh  with  the  gear  to  be  formed. 
It  is  made  of  hardened  tool  steel  and  is  ground  on  one  face, 
which  face  is  set  as  shown  in  the  end  view,  so  that  it  is  in  the 
plane  of  the  axis  of  the  work.  By  means  of  the  train  of  gear- 
ing just  described,  cutter  N  may  be  caused  to  revolve  in  uni- 
son with  the  work  as  if  it  were  in  mesh  with  the  latter  after 
the  teeth  have  been  cut. 


Fig.  54.   Shaving  Tool  and  Thread  Roll  on  an  "Acme"  Multiple- 
spindle  Automatic 

Driving  center  G  and  the .  front  bearing  of  gear  H  are  sup- 
ported in  a  sliding  bushing  0  seated  in  the  body  P  of  the 
tool.  A  plunger  Q  in  the  shank  of  the  tool  is  pressed  by  a 
long  and  stiff  spring  against  the  end  of  the  bearing  of  gear  H. 
This  serves  to  keep  G  pressed  into  the  hole  in  the  work.  As 
the  tool  advances  over  the  work,  center  G  and  gear  H  are 
forced  back  with  relation  to  the  holder,  remaining  stationary 
so  far  as  endwise  movement  is  concerned  with  relation  to  the 
work.  The  thrust  between  Q  and  the  end  of  H  is  taken  by  a 
hardened  ball-pivot  bearing  as  shown,  so  that  there  is  little 
friction.  The  extended  lip  on  the  bushing  0  is  simply  for  the 
purpose  of  providing  the  long  keyway  shown,  which  engages 


CUTTING  HELICAL  GEARS 


325 


a  pin  in  the  body  P  to  prevent  0  from  turning.  When  the 
tool  is  not  in  contact  with  the  work,  screw  R  limits  the  outward 
movement  of  G,  H,  and  0  produced  by  spring  plunger  Q. 

Operation  of  Cutting  the  Teeth.  —  Consider  now  that  there 
is  a  gear  blank  in  the  machine  with  the  teeth  all  cut,  but  not 


Machinery 


Fig.  55.  Tool  for  Generating  Teeth  of  Helical  Gears  in  Automatic  Screw 

Machine 

yet  severed  from  the  bar,  and  suppose  the  cutter  N  to  be  meshed 
with  it  as  shown  at  D  in  Fig.  56.  Suppose  further  that  the 
spindle  of  the  machine  has  been  stopped.  If  now  the  turret- 
slide  be  moved  forward  or  back  from  the  position  shown,  so 
that  the  generating  tool  is  moving  forward  or  back  over  the 


326 


SCREW  MACHINE  PRACTICE 


work,  center  G  and  gear  H  remain  stationary  with  reference  to 
the  work,  but  move  back  and  forth  with  relation  to  the  tool- 
holder.  This  axial  movement  of  gear  H  will  evidently  rotate 
helical  gear  /,  which,  through  the  train  of  spur  gears  K,  L, 
and  M  will  rotate  the  cutter  N.  The  ratio  of  this  train  of  gear- 
ing is  such  that  the  rotary  movement  given  to  N  by  the  longi- 
tudinal movement  of  the  tool-holder  in  either  direction  keeps 


CENTERING 

AND 

FACING 


_  CUTTING 
THE  TEETH 


COUNTER- 
BORING 


REMOVING 
BURRS  WITH 
FORM  TOOL 


CUTTING  OFF 


Machinery 


Fig.  56.   Successive   Operations  on  Helical  or  Spiral  Gears  produced  in 
Automatic  Screw  Machine 

it  exactly  in  step  with  the  teeth  of  the  work.  Thus  the  move- 
ment of  the  turret-slide  rolls  the  cutter  on  the  work  just  as 
if  the  cutter  were  mounted  perfectly  free  on  its  axis  and  were 
rolled  by  the  teeth  of  the  work,  instead  of  through  the  train 
of  gearing  described. 

Consider  further,  with  the  cutter  and  the  work  set  in  the 
relation  shown  in  Fig.  56,  that  the  turret-slide  of  the  machine 
is  fixed  in  position,  but  that  the  spindle  and  the  work  is  ro- 
tated. The  rotation  of  the  gear  revolves  the  three-cornered 


CUTTING  HELICAL  GEARS  327 

driving  center  G,  which,  in  turn,  transmits  its  motion  to  gear 
H  (Fig.  55)  and  thence  to  gears  /,  K,  L,  M,  and  cutter  N. 
The  ratio  of  this  train  of  gearing  is  again  such  that  the  rotary 
movement  thus  given  the  cutter  is  in  the  proper  ratio  to  keep 
the  latter  in  step  with  the  teeth  cut  in  the  work,  so  that  the 
work  and  cutter  revolve  together  as  if  they  were  a  pair  of  heli- 
cal gears  driving  each  other,  with  no  connection  through  the 
train  of  gearing. 

It  has  thus  been  shown  that  the  cutter  will  be  kept  in  step 
with  the  work,  if  the  tool  is  moved  axially  back  and  forth 
over  the  work  while  the  latter  is  stationary.  It  has  also  been 
shown  that  the  cutter  will  keep  in  mesh  with  the  work,  while 
the  latter  is  revolving  and  the  turret-slide  and  the  tool  are 
stationary.  Since  the  cutter  and  work  are  kept  in  step  under 
these  two  conditions  separately,  they  are  still  in  step  when  the 
two  movements  are  combined.  This  tool  and  its  arrange- 
ment of  gearing  can  thus  be  moved  back  and  forth  over  the 
revolving  work  without  throwing  the  teeth  in  the  cutter  and 
the  teeth  in  the  work  out  of  step  with  each  other,  assuming 
that  the  tool  is  not  moved  back  so  far  that  driving  center  G 
loses  its  contact  with  the  work,  as  the  proper  meshing  of  the 
cutter  depends  upon  the  driving  connection  between  G  and  the 
blank.  If  G  is  ever  moved  back  out  of  contact  with  the  blank, 
this  connection  is  broken,  and,  when  the  cutter  is  again  moved 
forward  onto  the  work,  it  will  probably  be  found  out  of  step. 

The  action  of  cutter  N  will  be  readily  understood,  now  that 
the  method  of  driving  has  been  explained.  The  face,  which 
is  in  the  plane  xx  of  the  axis  of  the  work,  as  shown  in  the  end 
view,  is  the  cutting  edge.  As  the  tool  is  forced  onto  the  work, 
this  revolving  cutting  edge,  having  the  exact  shape  of  the  helical 
gear  which  is  to  engage  with  the  work,  cuts  teeth  of  that  exact 
shape  on  the  blank  as  it  is  gradually  forced  over  it.  The  opera- 
tion is  an  example  of  the  molding-generating  principle,  the 
cutter  N  molding  the  proper  surface  to  mesh  with  its  own 
teeth. 

Details  of  Generating  Tool.  —  The  shank  of  the  tool  is  made 
very  long,  as  this  permits  the  use  of  a  spring  for  plunger  Q 


328  SCREW  MACHINE  PRACTICE 

which  is  long  enough  so  that  its  pressure  will  not  be  materially 
greater  when  the  cutter  is  pushed  clear  over  the  work  at  the 
completion  of  the  cut,  than  when  center  G  first  enters  the  hole 
in  the  work.  If  the  pressure  should  materially  increase,  there 
would  be  danger  that  G  might  be  pressed  further  into  the 
edge  of  the  hole,  thus  disturbing  the  axial  relation  of  G  and 
the  blank,  and,  consequently,  throwing  the  cutter  and  the  work 
out  of  step  with  each  other  by  that  amount.  The  use  of  the 
long  spring  prevents  such  trouble. 

The  cutter  spindle  5  is  mounted  in  bronze-bushed  bearings 
in  front  and  back  plates  T  and  U,  which  are  clamped  together 
and  to  the  body  P  of  the  tool  by  studs  and  nuts  V.  These 
studs,  as  shown  in  the  sectional  view,  pass  through  elongated 
slots  in  the  body,  so  that  the  cutter  spindle  may  be  adjusted 
for  a  larger  or  smaller  diameter  of  work  by  means  of  set-screws 
W,  the  adjustment  being  locked  by  nuts  V.  This  adjust- 
ment would,  of  course,  disturb  somewhat  the  correct  meshing 
of  gears  L  and  M.  Gear  L  is,  therefore,  mounted  on  a  stud  X 
which  floats  in  an  enlarged  hole  in  the  body,  and  so  may  be 
adjusted  by  means  of  suitable  set-screws  which  bring  it  into 
proper  mesh  with  both  M  and  K.  The  shaft  on  which  the 
latter  is  mounted  is  also  carried  in  a  sliding  block  F,  by  means 
of  which  gears  /  and  H  can  be  moved  into  closer  or  freer 
mesh.  After  the  cutter  has  been  set  to  the  proper  diameter  for 
the  work,  the  whole  system  of  gearing  may  thus  be  adjusted 
to  mesh  properly.  It  is  advisable  to  have  as  little  backlash 
as  possible  between  the  cutter  and  the  driving  center  to  pre- 
vent the  former  from  jumping  or  chattering  when  first  begin- 
ning the  cut.  When  there  is  much  backlash,  the  ends  of  the 
teeth  where  the  cut  begins  are  not  formed  to  quite  the  proper 
shape.  While  there  is  no  great  harm  in  this  in  the  case  of 
a  helical  gear,  in  which  the  contact  takes  place  in  the  center  of 
the  face,  it  gives  a  poor  appearance  to  the  work,  and  so  should 
be  avoided. 

The  thrust  of  the  revolving  work,  pressing  down  on  the 
cutter  when  the  tool  is  in  action,  is  taken  by  a  ball  bearing 
at  Z.  This  is  the  only  point  where  there  would  be  any  great 


CUTTING  HELICAL  GEARS  329 

danger  of  excessive  friction,  so  that  the  probability  of  G 
slipping  in  the  work,  due  to  too  great  a  resistance  in  the 
mechanism  it  has  to  drive,  is  obviated.  As  previously  ex- 
plained, the  cutting  edge  of  the  cutter  must  be  in  the  plane  of 
the  center-line  of  the  work.  In  the  tool  shown,  no  special  pro- 
vision is  made  for  maintaining  this  condition.  As  the  face  of 
the  cutter  is  sharpened,  it  is  necessary  to  pack  it  out  with 
filling  washers.  In  later  designs,  adjustments  are  provided 
for  bringing  the  cutting  point  on  a  line  with  the  center. 

Order  of  Operations  in  Making  the  Gears.  —  The  first 
operation  after  feeding  the  stock  is  centering  and  facing,  as 
shown  at  A,  Fig.  56.  This  is  done  with  a  tool  held  in  the 
turret.  The  turret  is  next  revolved  two  holes,  and  the  drill 
is  brought  into  action.  Then  the  turret  is  revolved  again  and 
the  hole  is  reamed.  The  reamer  is  mounted  in  a  "floating 
holder"  which  enables  the  reamer  to  be  centered  accurately, 
so  that  it  will  cut  to  size  and  take  off  an  equal  amount  with 
all  of  its  teeth.  While  the  drilling  and  reaming  are  going  on, 
the  blank  is  being  formed  by  a  circular  form  tool  mounted  in 
the  front  cross-slide,  as  shown  at  B  and  C.  The  operation  of 
cutting  the  teeth  at  D  has  already  been  described.  At  £,  the 
hole  is  count erbored.  This  counterboring  incidentally  re- 
moves the  marks  made  by  the  sharp  corners  of  driving  center 
G.  At  F,  the  completed  piece  is  severed  from  the  bar.  While 
the  counterboring  is  in  progress,  and  during  the  first  part  of 
the  cutting-off  operation,  the  front  form  tool,  as  shown  at  E 
and  F,  is  again  brought  down  to  clean  off  the  burrs  produced 
by  the  gear-cutting  tool.  The  gear  proper  has  a  face  width  of 
0.187  incn  and  a  diameter  of  0.421  inch.  The  material  is  brass, 
and  the  time  for  making  one  gear  complete,  22  seconds. 

Measuring  Screw  Machine  Chips.  —  It  is  the  practice  of 
some  screw  machine  operators  to  measure  the  thickness  of  the 
chips  in  order  to  determine  the  feeds  of  the  tools.  This  prac- 
tice is  misleading  because  of  the  tendency  of  the  metal  to 
compress  in  one  direction  and  swell  and  stretch  in  the  other, 
when  separated  from  the  bar  by  the  cutter.  In  order  to  ob- 
tain data  on  the  difference  between  the  feed  of  the  cutter  and 


330  SCREW  MACHINE  PRACTICE 

the  thickness  of  the  chips,  some  tests  were  made  on  a  Brown  & 
Sharpe  automatic  screw  machine.  A  cam,  the  exact  size 
and  travel  of  which  was  known,  was  placed  on  the  machine, 
and  the  machine  was  geared  to  rotate  the  cam  at  a  given  speed. 
The  exact  speed  of  the  spindle  was  also  determined,  and  in 
this  way  the  exact  feed  of  the  cutter  was  known. 

These  tests  showed  that  a  form  tool,  J  inch  wide,  having  a 
feed  of  o.oo i  inch  per  revolution,  cut  a  chip  which  measured 
0.0025  inch  when  cutting  brass,  while  a  form  tool  f  inch  wide, 
with  a  feed  of  0.0015  inch  per  revolution,  cut  a  continuous 
chip  0.005  mcri  thick.  A  cut-off  tool  f  inch  wide,  cutting  brass 
and  fed  o.ooi  inch  per  revolution,  produced  chips  from  0.0015 
to  0.002  inch  thick.  The  proportions  between  the  feed  and  the 
chip  for  the  turret  tools  were  slightly  greater  than  for  the 
cross-slide  tools ;  that  is,  the  chip  expanded  slightly  more.  The 
tests  for  steel  indicated  a  smaller  expansion  than  for  brass. 
Often  a  cam  designer  is  criticized  by  the  operators  for  providing 
excessive  feeds,  when  this  is  not  really  the  case,  the  apparent 
error  being  due  to  the  erroneous  method  used  by  the  operators 
in  measuring  the  feed.  The  error  that  would  result  in  the 
design  of  cams,  if  the  draftsman  worked  to  data  obtained  by 
measuring  the  chips  is,  however,  apparent. 

Speeds  and  Feeds.  —  The  following  information  on  the 
speeds  and  feeds  for  automatic  screw  machine  operation  is 
intended  only  as  a  general  guide,  since  both  the  feed  and  speed 
are  often  affected  considerably  by  the  nature  of  the  operations, 
variations  in  cutting  qualities  of  tools  made  from  different 
kinds  of  steel,  and  differences  in  degree  of  hardness  of  material 
of  the  same  general  class.  The  type  and  general  condition  of 
the  machine  that  is  used  may  also  be  important  factors. 

The  feeds  and  speeds  given  in  the  accompanying  table  are 
not  intended  to  represent  either  the  minimum  or  maximum 
in  any  case,  but  the  average  range  of  feeds  and  speeds  used 
on  machines  of  ordinary  size.  In  referring  to  this  table,  it  is 
important  to  bear  in  mind  that  the  rate  of  feed  per  revolution 
is  often  affected  considerably  by  the  speed,  some  automatic 
screw  machines  being  naturally  adapted  for  comparatively 


SPEEDS   AND   FEEDS 


331 


Ordinary  Ranges  of  Speeds  and  Feeds  for  Automatic  Screw  Machines 


Material 

Type  of 
Cutting 
Tool 

Steel  used 
for  Tools 

Surface  Speed, 
Feet  per 
Minute 

Feed  per 
Revolution, 
Inch 

Box-tool 
Box-tool 

Carbon 
High-speed 

160-180 
225-250 

0.004    to  0.015 

Hollow  Mill 
Hollow  Mill 

Carbon 
High-speed 

160-180 
225-250 

0.005    to  0.017 

Brass    • 

Forming 
Forming 

Drills 

Carbon 
High-speed 

Carbon 

150-175 
200-275 

160-180 

0.0008  to  0.003 
0.003    to  0.015 

Reamers 
Reamers 

Dies 

Carbon 
High-speed 

Carbon 

115-125 
145-160 

4.0—6"; 

0.007    to  0.030 

Dies 

High-speed 

80—130 

Cutting-off 

Carbon 

150-175 

0.0015  to  0.004 

Box-tool 
Box-tool 

Carbon 
High-speed 

80-90 
100-130 

0.003    to  o.oio 

Hollow  Mill 
Hollow  Mill 

Carbon 
High-speed 

80-90 
100-130 

O.OO4      tO  O.OI2 

Gun 
Screw    < 

Forming 
Forming 

Cutting-off 

Carbon 
High-speed 

75-90 
90-125 

O.OOO5  tO  O.OO2O 
O  OOI2  to  O  OO2C 

Iron 

Drills 
Drills 

Dies 

Carbon 
High-speed 

60-70 
100-125 

2C—  5O 

O.OO2      tO  O.OIO 

Reamers 
Reamers 

Carbon 
High-speed 

35-40 
60-75 

0.008     tO  0.020 

Box-tool 
Box-tool 

Carbon 
High-speed 

35-45 
45-60 

0.003    to  0.007 

Drill 
Rod 
and 

TV»r»l 

Hollow  Mill 
HoUow  Mill 

Forming 
Dies 

Carbon 
High-speed 

High-speed 
High-speed 

35-45 
45-60 

45-60 
IC-2S 

0.0035  to  0.008 

O.OOO2  tO  O.OOIO 

Steel 

Drills 
Drills 

Carbon 
High-speed 

30-40 
40-60 

0.002     tO  O.OIO 

Reamers 
Reamers 

Carbon 
High-speed 

20-25 
30-40 

0.006    to  0.015 

high  speeds  and  fine  feeds,  whereas  other  machines  rotate  the 
work  more  slowly,  but  are  capable  of  heavier  feeds.  The  feed 
for  box-tools  not  only  varies  for  different  materials,  but  should 


332  SCREW   MACHINE   PRACTICE 

be  selected  with  reference  to  the  thickness  of  the  chip  or  the 
depth  of  the  cut.  The  feed  for  forming  tools  should  be  varied 
in  accordance  with  the  width  of  the  tool  and  the  diameter  of 
the  smallest  part  to  be  formed.  In  general,  a  tool  from  about 
J  to  y3e  inch  wide  is  adapted  to  the  coarsest  feed.  For  tools 
that  are  either  very  much  narrower  or  wider,  the  feed  should 
be  reduced  accordingly.  The  effect  which  the  tool  width  and 
the  minimum  diameter  have  upon  the  feed  account  for  the 
wide  range  of  feeds  given  in  the  table  for  forming  tools. 

The  following  general  information  on  feeds  and  speeds  is 
given  by  the  Brown  &  Sharpe  Mfg.  Co.  The  feeds  and  speeds 
referred  to  are  merely  intended  as  a  general  guide,  and,  in  order 
to  obtain  satisfactory  results,  it  is  necessary  to  use  an  ample 
supply  of  good  cutting  oil  or  cooling  lubricant,  such  as  lard 
oil. 

Speeds  and  Feeds  for  Brass.  —  For  brass  of  ordinary 
quality,  the  machine  can  run  at  its  fastest  speed.  In  the  case 
of  a  No.  oo  machine,  the  maximum  spindle  speed  is  2400 
revolutions  per  minute,  and  the  largest  diameter  that  can  be 
turned  is  -IQ  inch,  so  that  the  maximum  surface  speed  is  197 
feet  per  minute.  On  the  Nos.  o  and  2  machines,  the  maxi- 
mum speeds  are  294  and  275  feet  per  minute,  respectively. 
Hollow  mills  when  used  on  brass  can  be  given  a  feeding  move- 
ment of  from  0.006  to  0.015  inch  per  revolution,  the  amount 
depending  upon  the  depth  of  the  cut.  The  feed  of  box-tools 
for  finishing  brass  should  be  about  o.oio  inch  per  revolution, 
and,  for  cutting-off  tools,  from  0.0015  to  0.002  inch  per  revolu- 
tion, the  feed  being  reduced  as  the  tool  reaches  the  center  of 
the  work.  Forming  tools  are  usually  fed  from  0.0008  to  0.0015 
inch  per  revolution,  although  the  feeding  movement  is  reduced 
to  0.0005  inch,  in  some  cases.  Drills  varying  from  J  to  J  inch 
in  diameter  can  be  fed  from  0.003  to  0.006  inch  per  revolution ; 
for  smaller  drills,  the  feeds  are  reduced  from  0.003  to  0.0015 
inch. 

Speeds  and  Feeds  for  Gun  Screw  Iron.  —  Gun  screw  iron, 
when  using  a  fine  feed,  can  be  given  a  speed  of  from  80  to  90 
feet  per  minute  for  either  hollow  mills,  box-tools,  cutting-off 


SPEEDS  AND  FEEDS  333 

tools,  or  forming  tools.  Hollow  mills  for  roughing  can  be  fed 
from  0.004  to  0.012  inch  per  revolution.  Box-tools  for  finish- 
ing, when  taking  a  finishing  cut  of  average  depth,  which  is 
about  o.oio  inch,  can  be  fed  from  o.oio  to  0.012  inch  per 
revolution,  but  the  feed  should  be  reduced,  if  the  tool  is  to  be 
used  for  facing  shoulders  or  for  similar  operations.  Cutting- 
off  tools  can  be  fed  from  0.0012  to  0.0017  inch  per  revolution. 
For  forming  tools,  the  feed  usually  varies  from  0.0002  to  o.ooi 
inch,  the  amount  depending  upon  the  width  and  finished  size 
of  the  work.  Drills  should  be  fed  about  one-third  lower  than 
for  brass,  and,  when  drilling  deep  holes,  the  feed  should  be 
reduced  towards  the  bottom.  Dies  and  taps,  when  operating 
on  gun  screw  iron,  should  not  have  a  cutting  speed  exceeding 
30  feet  per  minute. 

Speeds  and  Feeds  for  Machine  Steel  and  Drill  Rod.  —  Soft 
machine  steel  can  be  cut  off  and  formed  at  a  speed  of  about 
80  feet  per  minute,  but,  for  threading  operations,  this  should 
be  reduced  to  from  20  to  30  feet  per  minute.  The  feed  per 
revolution  can  usually  be  about  the  same  as  for  iron.  It  is 
often  necessary  to  run  bronze  at  about  the  same  speed  as 
machine  steel.  Drill  rod  is  often  operated  at  speeds  varying 
from  50  to  60  feet  per  minute,  but  only  when  using  very  fine 
feeds.  The  feed  usually  ranges  from  0.003  to  0.007  incn  per 
revolution.  For  threading  drill  rod,  the  speed  should  not 
exceed  15  or  20  feet  per  minute. 

It  is  the  practice  of  the  Brown  &  Sharpe  Mfg.  Co.  to  use 
fast  speeds  and  fine  feeds  for  most  operations,  although  the 
relation  of  the  feed  and  speed  is  often  varied  to  suit  different 
classes  of  work.  The  speeds  and  feeds  referred  to  in  the  fore- 
going are  intended  for  carbon  steel  tools.  When  using  high- 
speed steel,  these  speeds  can  be  increased  approximately  50 
per  cent  for  mild  steel  and  from  30  to  35  per  cent  for  drill 
rod,  assuming  that  the  same  feeds  are  used. 

Feed  for  Thread  Rolling.  —  When  rolling  threads,  the 
feed  is  varied  in  accordance  with  the  diameter  of  the  blank  to 
be  threaded  and  the  number  of  threads  per  inch.  The  type 
of  holder  used  also  affects  the  feed.  If  the  roll  is  held  in  a  holder 


334  SCREW   MACHINE   PRACTICE 

attached  to  the  cross-slide  and  is  presented  either  tangen- 
tially  or  radially  to  the  work,  it  can  be  fed  at  a  faster  rate  than 
if  it  is  held  in  a  swing  tool,  because,  in  the  former  case,  it  is 
held  more  rigidly.  The  feeds  for  thread  rolling  may  vary  from 
0.0005  to  o.oio  inch  per  revolution,  and,  in  some  cases,  coarser 
feeds  are  employed.  When  using  a  cross-slide  type  of  roll- 
holder,  the  following  feeds  would  prove  satisfactory  on  a  Brown 
&  Sharpe  machine :  For  80  threads  per  inch  and  a  blank  di- 
ameter of  J  inch,  o.oo6-inch  feed ;  for  a  blank  diameter  of 
\  inch,  o.oo8-inch  feed ;  for  a  blank  diameter  of  i  inch,  .010- 
inch  feed.  For  40  threads  per  inch  and  a  blank  diameter  of 
\  inch,  0.003 -inch  fee(i  >  f°r  a  blank  diameter  of  \  inch,  0.005- 
inch  feed ;  for  a  blank  diameter  of  i  inch,  o.ooy-inch  feed. 
For  24  threads  per  inch  and  a  blank  diameter  of  J  inch,  0.0005- 
inch  feed;  for  a  blank  diameter  of  |  inch,  o.oo25-inch  feed; 
for  a  blank  diameter  of  i  inch,  o.oo45-inch  feed.  When  using 
a  holder  of  the  swing  type,  these  feeding  movements  should  be 
reduced  about  25  or  30  per  cent. 

Feeds  for  Drilling.  —  When  selecting  the  feeds  for  drills, 
the  diameter  of  the  drill  should  be  considered.  For  instance, 
when  drilling  brass,  a  drill  -jV  inch  in  diameter  should  be  given 
a  feed  of  about  0.0018  inch  per  revolution;  if  the  drill  di- 
ameter were  \  inch,  the  feed  should  be  increased  to  approxi- 
mately 0.003  or  0.004  incn ;  ^  the  drill  diameter  were  \  inch, 
the  feed  should  be  from  0.005  to  0.007  mcn ;  and,  if  the  drill 
diameter  were  \  inch,  it  should  be  from  0.007  to  o.oio  inch 
per  revolution,  and,  for  larger  sizes,  still  coarser  feeds  could 
be  employed. 

When  using  Brown  &  Sharpe  automatic  screw  machines, 
the  best  results  are  generally  obtained  by  employing  light 
feeds  for  drills  and  rather  high  peripheral  velocities.  High- 
speed steel  drills  are  preferable  for  drilling  Norway  iron,  machine 
steel,  tool  steel,  etc.,  but  ordinary  carbon  steel  drills  are  suit- 
able for  brass  and  similar  materials,  when  the  cutting  speeds 
do  not  exceed  those  given  in  the  table.  When  the  cutting 
speed  is  relatively  low,  the  feed  can  be  increased  accordingly, 
but  it  is  more  satisfactory  in  general  practice  to  use  a  fine  feed 


SPEEDS   AND   FEEDS  335 

and  a  high  speed,  as  a  straighter  hole  can  be  produced  by  this 
method. 

Counterboring  and  Reaming  Feeds.  —  The  surface  speed 
for  counterboring  should  be  slightly  less  than  the  speed  for 
drilling.  The  feed  depends  upon  the  type  of  counterbore  used, 
as  well  as  the  material  being  cut  and  the  depth  of  the  cut. 
When  using  a  counterbore  having  three  cutting  edges,  the  feed 
for  brass  usually  varies  from  about  0.003  to  0.008  inch  per 
revolution,  the  amount  depending  upon  the  diameter  of  the 
counterbore  and  the  depth  of  the  cut.  For  machine  steel, 
the  feed  would  be  somewhat  less,  ranging  from  about  0.002  to 
0.006  inch  per  revolution.  The  feed  used  for  reaming  depends 
not  only  upon  the  diameter  of  the  reamer  and  the  material 
being  reamed,  but  also  upon  the  allowance  left  for  the  reaming 
operation,  and  varies  widely,  as  shown  by  the  table.  In  gen- 
eral, the  allowances  should  be  as  follows :  Diameter  of  hole, 
|  inch,  allowance,  0.005  incn  >  diameter  of  hole,  J  inch,  allow- 
ance, 0.007  inch;  diameter  of  hole,  ^  inch,  allowance,  o.oio 
inch;  diameter  of  hole,  i  inch,  allowance,  0.016  inch. 


INDEX 


ACCELERATING  type  of  reaming 

attachment,  207 

Accelerating  type   of  cross-drilling   at- 
tachment, 202 
Acme  accelerating  reaming  attachment, 

207 

Acme  cross-drilling  attachment,  202 
Acme  milling  attachments,  209 
Acme  multiple-spindle  automatic,  39 
adjustment  of,  170 
camshaft,  44 
camshaft  speed-changing  mechanism, 

45 

feeding  stock  through  spindle,  51 
general  description,  39 
indexing  mechanism,  49 
mechanism  for  threading,  52 
operation  of  cross-slides,  48 
operation  of  spindle  chuck,  50 
operations  on,  290 
speed  of  main  driving  shaft,  47 
spindle-driving  mechanism,  43 
standard  tool  positions,  41 
Acme  over-cut  box-tools,  98 
Acme  thread-rolling  tool,  322 
Adjustment   of   automatic   screw   ma- 
chines, 148 

Allowances  for  reaming,  125 
Allowances  for  shaving  cuts,  130,  131 
Aluminum,   use   of  roller  supports  in 

turning,  109 

Angle  of  centering  tool,  115 
Angles,  cutting,    for   box-tool   cutters, 

in 

Application   of    automatic   screw   ma- 
chines, general,  7 
Assembling  parts  in  automatic  screw 

machine,  304 

Attachment,    for   hobbing    worm    and 
spiral  gears,  215 


Attachment  for  self-opening  dies,  137 
for  drilling,  200 
for  forming  squares   and  hexagons, 

213 

for  milling,  209 
for  screw  slotting,  197 
magazine  feeding,  219 
Automatic,  application  of  term,  2 
Automatic    screw    machines,     adjust- 
ment, 148 

advantages  of  single-  and  multiple- 
spindle  designs,  8 
classification,  4 
development  of  multiple-spindle  type, 

6 

development  of  single-spindle  type,  5 
general  features,  3 
multiple-spindle  designs,  39 
single-spindle  designs,  n 

BACK-SLIDE  cam,  method  of  lay- 
ing out,  241 

Boring  and  recessing  tools,  125 
Box-tool  cutters,  cutting  angles,  i  T  i 

holding  and  adjusting,  106 

methods  of  applying,  104 

radial  and  tangential  positions  for, 
104 

size  of  steel,  113 
Box-tools,  94 

over-cut  type,  98 

spring-releasing  type,  99 

setting,  on  Acme  machine,  178 

taper  turning,  101 
Box-tool  work  supports,  108 

holding  and  adjusting,  109 

position  relative  to  cutter,  112 
Brass,  speeds  and  feeds  for,  332 
Brown  &  Sharpe  burring  attachment, 
205 


338 


INDEX 


Brown  &  Sharpe  cross-drilling  attach- 

ment, 201 
Brown  &  Sharpe  index  drilling  attach- 

ment, 200 
Brown  &  Sharpe  screw  machines,  deflec- 

tor for  chips,  1  8 

general  method  of  setting  up,  158 
general  description,  n 
operation  of  cross-slide,  15 
operation  of  turret-slide,  16 
reversal  of  spindle  for  threading,  18 
sample  record  of  cam  and  tool  equip- 

ment, 159 

spindle  speed  changes,  18 
stock-feeding     and     chuck-operating 

mechanism,  15 
Brown  &  Sharpe  screw  slotting  attach- 

ment, 197 
Brown  &  Sharpe  tap  and  die  revolving 

attachment,  206 

Brown  &  Sharpe  taper-turning  tool,  102 
Brown  &  Sharpe  turret  .drilling  attach- 

ment, 205 
Burring  attachment,  205 


blanks,    Brown     &     Sharpe, 


234 


Cam  circumference,  proportioning,  233 
Cam  design,  allowance  for  tool  clear- 

ance, 247 

effect  of  cutting  speed  on,  225 
general  procedure,  225 
lobe  for  thread  cutting,  243 
rise  for  drilling,  255 
Cams  for  making  a  screw,  227 
Cams  for  recessing,  laying  out,  253 
Cams  for  screw  machines,  designing,  224 
Cams,    function    of     lead,    front-slide 
and  back-slide,  on  B.  &  S.  Machine, 
224 

Cam-lever  templets,  use  of,  250 
Cast   iron,   use   of   roller   supports   in 

turning,  109 

Centering  and  facing  tools,  114 
Centering-tool  holder,  115 
Centering  tool,  included  angle  of  point, 

"5 
Centering  tools  and  drills,  setting,  154 


Change-gears,  table  of  No.  oo  Brown  & 

Sharpe  machine,  233 
Chicago    screw    machine,   general   de- 
scription, 35 

camshaft  and  main  cam,  36 
chuck  feeding  mechanism,  36 
feeding  movements  for  tools,  38 
method  of  cutting  threads,  37 
operation  of  cross-slides,  37 
turret  mechanism,  36 
Chips,   measurement  of,   to  determine 

feed,  329 

Circular  forming  and  cutting-off  tools, 
holder  for,  88 
setting,  149 
Circular    forming    tools,    methods    of 

applying,  85,  89 
Clearance  for  circular  tools,  90 
Clearance  for  tools  in  laying  out  cams, 

247 
Cleveland    automatic,    adjustment    of, 

161 

chuck-operating  mechanism,  22 
examples  of  work  on,  281 
feed-regulating  drum,  29 
general  description,  20 
operation  of  cross-slide,  28 
spindle-driving  mechanism,  22 
stock-feeding  mechanism,  25 
turret  and  turret-slide,  26 
variable  feeding  mechanism,  28 
Cleveland  independent  cutting-off  at- 
tachment, 211 

Cleveland    magazine    feeding    attach- 
ments, 219 

Cleveland  silent  die-holder,  135 
Cleveland  slotting  and  slabbing  attach- 
ment, 199 
Cleveland    thread-rolling    attachment, 

321 
Compensating  stops  for  multiple-spindle 

machines,  60 
Cone-point  turning  in  screw  machine, 

274 

Counterbores,  amount  of  taper  for,  120 
holders,  123 

location  of  cutting  edge,  120 
reasons  for  defective  operation,  119 


INDEX 


339 


Counterbores  and  reamers,  setting,  154 
Counterboring  and  drilling  from  cross- 
slide,  266 

Counterboring  and  reaming  feeds,  335 
Counterboring  tools,  119,  122 
Cross-drilling  attachment,  201 
Cross-drilling   attachment   of   opposed 

spindle  type,  204 

Cross-drilling,  example  of  work  requir- 
ing, 294 

Cutters  for  box-tools,  104 
cutting  angles,  in 
holding  and  adjusting,  106 
position  relative  to  work   supports, 

112 

size  of  steel,  113 
Cutting-off  and  forming  tools,  rake  of, 

93 

setting  on  Acme  machine,  177 
Cutting-off  attachment,  Cleveland,  211 
Cutting-off  tool-holder,  universal,  91 
Cutting-off  tools,  92 

inclination  of  cutting  edge,  229 

thickness  of  blade,  93 

DAVENPORT  multiple-spindle  auto- 
matic, 55 

cam  equipment  for,  192 
compensating  stops,  60 
cross-slides  and  swinging  arms,  58 
driving  mechanism  for  camshaft,  58 
general  description,  55 
indexing  the  spindle  head,  60 
method  of  cutting  thread,  62 
method  of  driving  spindles,  55 
operation  of  tool  spindles,  56 
sample  record  of  operations,  193 
setting-up,  189 
speeds  and  feeds  recommended,  63 

Deep-hole  drilling,  designing  cam  for, 

257 

Die-  and  tap-holder,  telescopic,  136 
Die  and  tap  revolving  attachment,  206 
Die-holders,  133 

Cleveland  silent  type,  135 

releasing,  134 

Dies  and  taps,  setting,  155 
Dies,  attachment  for  self -opening,  137 


Dies  for  screw  machine  work,  132 
Drill-holder,  high-speed,  118 
Drill-holders  for  screw  machines,  118 
Drilling  and  Counterboring  from  cross- 
slide,  266 
Drilling  and  milling  attachment,  Acme, 

209 
Drilling  attachment,  cross-,  201 

index,  200 
Drilling,  feeds  for,  334 

laying  out  cams  for,  255 
Drill  rod,  speeds  and  feeds  for,  333 
Drills  and  centering  tools,  setting,  154 
Drills,  flat,  122 

for  screw  machine  work,  116 

END-MILLING  or  slotting  attach- 
ment, 211 
facing  and  centering  tools,  114 

pEED,    determining,    by    measuring 
chips,  329 

for  thread  rolling,  333 
Feeding  attachments,  magazine,  219 
Feeds  and  speeds,  330 

for  different  tools  and  materials,  331 
Feeds,  for  Counterboring  and  reaming, 

335 

for  drilling,  334 
Flat  forming  tool-holders,  90 
Flutes,  number  in  taps,  139 
Forming  and  cutting-off  tools,  rake  of, 

93 

setting,  on  Acme  machine,  177 
Forming  operations,  examples  of,  260 
Forming    tools,   methods   of   applying, 

85,89 

tool-holders  for  flat,  90 
Front-slide  cam,  method  of  laying  out, 

242 

gears,    helical   or    spiral,   cutting   in 
screw  machine,  323 

(~^UN  screw  iron,  speeds  and  feeds  for, 

332 
Gridley  multiple-spindle  automatic,  71 

camshaft  and  cams,  74 

feeding  movements,  73 


340 


INDEX 


Gridley    multiple-spindle    automatic, 
general  description,  71 

idle  movements,  73 

method  of  cutting  threads,  76 

tool-slide,  73 

Gridley   single-spindle   automatic,    ap- 
plication of  motor  drive,  35 

arrangement  of  cams,  33 

arrangement  of  turret,  30 

general  description,  30 

operation  of  forming  and  cutting-off 
tools,  33 

fjAYDEN     multiple-spindle     auto- 
matic, 64 
adjustable  cams  for  tool  spindles  and 

cross-slides,  68 

chuck-closing  mechanism,  66 
general  description,  64 
operation  of  master  cam,  66 
thread  cutting  operations,  71 
time  required  for  making  one  piece, 

69 
Helical  gears,  cutting  in  screw  machine, 

323 

Hexagon  and  square  forming  attach- 
ment, 213 
Holders,  for  centering  tools,  115 

for  circular  forming  and  cutting-off 

tools,  88 

for  counterbores,  123 
for  flat  forming  tools,  90 
for  reamers,  127 
Hollow  mills,  113 

Hollow  mills  or  box-tools,  setting,  153 
Hollow  roughing  mill,  98 

INDEX  drilling  attachment,  200 

KNURL-HOLDER,  double  type  for 
cross-slide,  143 

opening  and  closing  type,  143 
Knurling  tools,  140 
Knurls,  concave,  145 

different  methods  of  applying,  144 

spiral,  146 

straight,  145 


Knurl  teeth,  angles  for  different  mate- 

rials, 145 
calculating  depth  of,  145 

LEAD  CAM,  function  of,  on  Brown 

&  Sharpe  machine,  224 
method  of  laying  out,  for  Brown  & 
Sharpe  machine,  236 

MACHINE  steel,  speeds  and   feeds 

for,  333 

Magazine  feeding  attachments,  219 
Milling  attachments,  Acme,  209 
Multiple-    and    single-spindle    designs, 

relative  advantages,  8 
Multiple-spindle    screw    machine    de- 

velopment, 6 
Multiple-spindle  screw  machines,  39 


BRITAIN     multiple-spindle 
screw  machine,  76 
indexing  mechanism,  80 
spindle  construction,  78 
thread  cutting  mechanism,  82 
tool  slide,  79 
Non-releasing  type  of  die-holder,  133 

OPERATIONS  on  screw   machines, 

miscellaneous,  258 
pointing  end  of  work,  259 

PRODUCTION  rate,  calculating  for 
Acme  machine,  172 

RAISING    block    for    swing    tools, 

128 
methods    of    setting    on    Brown    & 

Sharpe  machines,  157 
Reamer  holders,  127 
Reamers  and  counterbores,  setting,  154 
Reamers  for  screw  machine  work,  125 
Reamers,  taper  of,  125 
Reaming  allowances,  125 
Reaming  and  counterboring  feeds,  335 
Reaming  attachment,  accelerated,  207 
Recessing  and  boring  tools,  125 
Recessing,  laying  out  cams  for,  253 
Recessing  operation,  265 


INDEX 


341 


Recessing  swing  tools,  129 

Record  of  cam  and  tool  equipment  on 

Brown  &  Sharpe  machine,  159 
Record    of    operations    on    Davenport 

machine,  193 
Releasing  die-holder,  134 
Roller  supports  for  box-tools,  95,  96, 

109,  in 

Rolling  threads  in  screw  machine,  314 
Roller  type  of  steadyrest,  113 
Rotary  magazine  attachment,  221 

gCREW     MACHINE,    adjustment, 

148 

cams,  designing,  224 
classification,  4 
development,  5 
general  features,  3 
multiple-spindle  designs,  39 
operations,  miscellaneous,  258 
origin  of  term,  i 
relative    advantages  of  single-   and 

multiple-spindle  designs,  8 
single-spindle  designs,  n 
use   of,  for  machining   and   assem- 
bling, 304 

Screw  slotting  attachments,  197 
Setting-up  automatic  screw  machines, 

148 
Shaving  operation,  allowances  for,  130, 

131 

Shaving  tools  for  screw  machines,  130 
Single-    and    multiple-spindle   designs, 

relative  advantages,  8 
Single-spindle  screw  machine  develop- 
ment, 5 

Slab  milling  attachments,  209 
Slotting  and  slabbing  attachment,  199 
Speeds  and  feeds,  330 

for  different  tools  and  materials,  331 
Spiral  gear-hobbing  attachment,  215 
Spiral  gears,  cutting  in  screw  machine, 

323 
Spiral  knurls,  determining  lead  of  teeth, 

147 
determining  number  of  teeth  around 

circumference,  146 
Spring-releasing  box-tools,  99 


Spring   screw  threading  dies,  making, 

132 

Square  and  hexagon  forming  attach- 
ment, 213 

Steadyrest  of  roller  type,  1 13 
Steel  for  box-tool  cutters,  size  of,  113 
Steel  for  box-tool  supports,  109 
Stop  for  stock,  setting,  152 
Supports,  work,  for  box- tools,  108 

holding  and  adjusting,  109 
Swing  tools,  for  turning,  128 

methods  of  setting  raising  block  for 
operating,  157 

raising  block  for,  128 

recessing,  129 

setting,  156 

TAP-  and  die-holder,  telescopic,  136    . 
Tap  and  die  revolving  attachment,  206 
Taps  and  dies,  setting,  155 
Taps,  chamfer  for  different  pitches,  139 
cutters  for  fluting,  139 
for  automatic  screw  machines,  138 
for  Norway  iron  and  machine  steel, 

140 

number  of  flutes  for,  139 
width  of  lands,  139 
Telescopic  die-  and  tap-holder,  136 
Templet  for  dividing  cam  circumfer- 
ence, 238 
Templet  for  laying  out  screw  machine 

cams,  235 

Templets,  use  of  cam-lever  type,  250 
Thread   cutting,  development  of  cam 

lobe  for,  243 

dies  for  screw  machines,  132 
number  of  revolutions  for,  229 
on  Acme  machine,  181 
on  Davenport  multiple-spindle  auto- 
matic, 192 

on    Gridley    multiple-spindle    auto- 
matic, 76 

on    Hayden    multiple-spindle    auto- 
matic, 71 
on    New    Britain    multiple-spindle 

automatic,  82 

reversal  of  spindle   for,  in  B.  &  S. 
machine,  18 


342 


INDEX 


Threading-die  holders,  133 

Threading    dies,    methods    of    making 
spring  screw  type,  132 

Thread  rolling,  Acme  type  of  holder 

for,  322 

attachment,  Cleveland,  321 
by  means  of  swing  tool,  320 
calculating  blank  diameter,  315 
Cleveland  attachment  for,  321 
feeds  for,  333 

holder  for  passing  roll  over  work,  319 
holder  for  passing  roll  under  work, 

320 

inclination  of  thread  on  roll,  315 
in  screw  machines,  314 
preparation  of  work  for,  318 
shape  of  thread  on  roll,  316 
size  of  thread  roll,  317 
steel  for  thread  rolls  applied  to  steel, 

3i5 
Thread  roll,  size  of,  317 


Tilting  magazine  attachment,  219 

rotary  type  of,  222 
Tool  clearance,  allowance  for,  in  cam 

design,  247 

Tool  equipment  for  screw  machines,  84 
Tool-holders  for  boring  and  recessing 

tools,  125 

Tool-holder,  universal  cutting-off,  91 
Turret  drilling  attachment,  205 

UNIVERSAL     cross-slide     knurling 

tool,   141 
Universal  cutting-off  tool-holder,  91 

VERTICAL  magazine  feeding  attach- 
ment, 220 


parts,    making,  in    screw 
machine,  271 
Worm  gear  bobbing  attachment,  215 


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